Ligurian Sea, northwestern Mediterranean Sea

J.CETACEAN
CETACEAN
RES. MANAGE.
11(1):31–40,
2009
J. J.
CETACEAN
MANAGE.11(1):31–40,
11(1):31–40,
2009
CETACEANRES.
RES.MANAGE.
MANAGE.
11(1):31–­­
40,2009
2010
3131
31
Seasonal
estimates
densities
and
predation
rates
cetaceans
Seasonal
Seasonalestimates
estimatesofof
ofdensities
densitiesand
andpredation
predationrates
ratesofof
ofcetaceans
cetaceans
the
Ligurian
Sea,
northwestern
Mediterranean
Sea:
an
initial
inin
inthe
theLigurian
LigurianSea,
Sea,northwestern
northwesternMediterranean
MediterraneanSea:
Sea:an
aninitial
initial
examination
examination
examination
S
L
C
JJOIRIS
,, A
LEXANDRE GANNIER
R
ENNEY
*,+*,+
+, +A
# AND
^ ^
# AND
SOPHIE
LARAN
, C,, LAUDE
JOIRIS
LEXANDRE
GG
ANNIER
ROBERT
D.D.
ENNEY
SOPHIE
OPHIE
LARAN
ARAN
CLAUDE
LAUDE
OIRIS
A
LEXANDRE
ANNIER
AND
ROBERT
OBERT
D.KK
K
ENNEY
Contact
e-mail:
[email protected]
Contact
Contacte-mail:
e-mail:[email protected]
[email protected]
*,+
+
#
^
ABSTRACT
ABSTRACT
ABSTRACT
The Ligurian Sea is one of the most attractive areas for cetaceans in the Mediterranean Sea, and is now included in a Marine Protected Area, the
The
Ligurian
Sea
is is
one
of of
thethe
most
attractive
areas
forfor
cetaceans
in in
thethe
Mediterranean
Sea,
and
is is
now
included
in in
a Marine
Protected
Area,
thethe
The
Ligurian
Sea
one
most
attractive
areas
cetaceans
Mediterranean
Sea,
and
now
included
a Marine
Protected
Area,
Pelagos Sanctuary. Despite a lower species diversity than in other parts of the world, because of their abundance, cetaceans are thought to represent
Pelagos
Sanctuary.
Despite
a lower
species
diversity
than
in in
other
parts
of of
thethe
world,
because
of of
their
abundance,
cetaceans
areare
thought
to to
represent
Pelagos
Sanctuary.
Despite
a lower
species
diversity
than
other
parts
world,
because
their
abundance,
cetaceans
thought
represent
significant consumers in this ecosystem. Surveys were conducted within the Pelagos Sanctuary from 2001 to 2004. Densities of five species:
significant
consumers
in in
this
ecosystem.
Surveys
were
conducted
within
thethe
Pelagos
Sanctuary
from
2001
to to
2004.
Densities
of of
five
species:
significant
consumers
this
ecosystem.
Surveys
were
conducted
within
Pelagos
Sanctuary
from
2001
2004.
Densities
five
species:
striped dolphin (Stenella coeruleoalba); fin whale (Balaenoptera physalus); sperm whale (Physeter macrocephalus); long-finned pilot whale
striped
dolphin
(Stenella
coeruleoalba);
finfin
whale
(Balaenoptera
physalus);
sperm
whale
(Physeter
macrocephalus);
long-finned
pilot
whale
striped
dolphin
(Stenella
coeruleoalba);
whale
(Balaenoptera
physalus);
sperm
whale
(Physeter
macrocephalus);
long-finned
pilot
whale
(Globicephala melas); and Risso’s dolphin (Grampus griseus), were estimated and converted to biomass. Total biomass density of cetaceans in the
(Globicephala
melas);
and
Risso’s
dolphin
(Grampus
griseus),
were
estimated
and
converted
to to
biomass.
Total
biomass
density
of of
cetaceans
in in
thethe
(Globicephala
melas);
and
Risso’s
dolphin
(Grampus
griseus),
were
estimated
and
converted
biomass.
Total
biomass
density
cetaceans
-2 (CV=28%) in winter (October to March) and 509kg km-2 (CV=16%) in summer (April to September).
Ligurian Sea was estimated as 93kg km
-2 (CV=28%)
-2 -2
-2 (CV=28%)
Ligurian
Sea
was
estimated
as as
93kg
kmkm
in in
winter
(October
to to
March)
and
509kg
kmkm
(CV=16%)
in in
summer
(April
to to
September).
Ligurian
Sea
was
estimated
93kg
winter
(October
March)
and
509kg
(CV=16%)
summer
(April
September).
-2 d-1 in winter, increasing to 10.4kg km-2 d-1 in summer, corresponding to a total
Daily predation rates by cetaceans were estimated as 2.9kg km
-2 -2
-2 -2
Daily
predation
rates
byby
cetaceans
were
estimated
as as
2.9kg
kmkm
d-1d-1
in in
winter,
increasing
to to
10.4kg
kmkm
d-1d-1
in in
summer,
corresponding
to to
a total
Daily
predation
rates
cetaceans
were
estimated
2.9kg
winter,
increasing
10.4kg
summer,
corresponding
a total
-2 y-1. The annual primary production required for cetaceans was estimated to be 12.6gC m-2 y-1, corresponding to 6annual ingestion of 2.4t km
-2 -2
annual
ingestion
of of
2.4t
kmkm
y-1y.-1The
annual
primary
production
required
forfor
cetaceans
was
estimated
to to
bebe
12.6gC
m-2m-2
y-1y,-1corresponding
to to
6- 6annual
ingestion
2.4t
. The
annual
primary
production
required
cetaceans
was
estimated
12.6gC
, corresponding
15% of the net primary production known for this area. Estimated cetacean predation on fish was similar to reported fisheries landings,
15%
15%of ofthethenetnetprimary
primaryproduction
productionknown
knownforforthis
thisarea.
area.Estimated
Estimatedcetacean
cetaceanpredation
predationononfish
fishwas
wassimilar
similarto toreported
reportedfisheries
fisherieslandings,
landings,
nevertheless, management of artisanal fisheries and accurate quantification of the resources they exploit will be necessary for the responsible
nevertheless,
management
of of
artisanal
fisheries
and
accurate
quantification
of of
thethe
resources
they
exploit
will
bebe
necessary
forfor
thethe
responsible
nevertheless,
management
artisanal
fisheries
and
accurate
quantification
resources
they
exploit
will
necessary
responsible
management of fisheries in this Mediterranean Marine Protected Area.
management
of of
fisheries
in in
this
Mediterranean
Marine
Protected
Area.
management
fisheries
this
Mediterranean
Marine
Protected
Area.
KEYWORDS: INDEX
INDEX OF
OF ABUNDANCE;
NUTRITION; FOOD/PREY;
FOOD/PREY; SANCTUARIES;
SANCTUARIES;FEEDING
FEEDINGGROUNDS;
GROUNDS;SURVEY
SURVEY-- VESSEL;
KEYWORDS:
ABUNDANCE;NUTRITION;
NUTRITION;
VESSEL;
KEYWORDS:
INDEX
OFOF
ABUNDANCE;
FOOD/PREY;
SANCTUARIES;
FEEDING
GROUNDS;
SURVEYVESSEL;
KEYWORDS:
INDEX
ABUNDANCE;
NUTRITION;
FOOD/PREY;
SANCTUARIES;
FEEDING
GROUNDS;
SURVEYVESSEL;
SURVEY
–
ACOUSTIC;
STRIPED
DOLPHIN;
FIN
WHALE;
SPERM
WHALE;
LONG-FINNED
PILOT
WHALE;
RISSO’S
DOLPHIN;
SURVEY
–– ACOUSTIC;
ACOUSTIC;
STRIPED
DOLPHIN;
FIN
WHALE;
SPERM
WHALE;
LONG-FINNED
PILOT
WHALE;
RISSO’S
DOLPHIN;
SURVEY
– ACOUSTIC;
STRIPED
DOLPHIN;
FIN
WHALE;
SPERM
WHALE;
LONG-FINNED
PILOT
WHALE;
RISSO’S
DOLPHIN;
SURVEY
STRIPED
DOLPHIN;
FIN
WHALE;
SPERM
WHALE;
LONG-FINNED
PILOT
WHALE;
RISSO’S
DOLPHIN;
MEDITERRANEAN SEA; NORTHERN HEMISPHERE
MEDITERRANEAN
SEA;
NORTHERN
HEMISPHERE
MEDITERRANEAN
SEA;
NORTHERN
HEMISPHERE
INTRODUCTION
INTRODUCTION
INTRODUCTION
Marine
mammals
often
play
key
roles
within
marine
Marine
Marinemammals
mammalsoften
oftenplay
playkey
keyroles
roleswithin
withinmarine
marine
ecosystems,
consequently
their
abundance
and
their
ecosystems,
ecosystems, consequently
consequently their
their abundance
abundance and
and their
their
distribution
can
have
important
effects
the
structure
and
distribution
distributioncan
canhave
haveimportant
importanteffects
effectsonon
onthe
thestructure
structureand
and
function
of
some
ecosystems
(Bowen,
1997;
Estes
et
al.,
function
functionofofsome
someecosystems
ecosystems(Bowen,
(Bowen,1997;
1997;Estes
Estesetetal.,
al.,
2006).
Nevertheless
their
role
as
top
predators
needs
to
2006).
2006).Nevertheless
Neverthelesstheir
theirrole
roleasastop
toppredators
predatorsneeds
needstotobebe
be
characterised
and
quantified
order
better
understand
characterised
characterisedand
andquantified
quantifiedinin
inorder
ordertoto
tobetter
betterunderstand
understand
their
habitat
use
and
identify
the
possible
impacts
human
their
theirhabitat
habitatuse
useand
andidentify
identifythe
thepossible
possibleimpacts
impactsofof
ofhuman
human
activities.
All
cetaceans
are
carnivores
and
in
many
marine
activities.
activities.All
Allcetaceans
cetaceansarearecarnivores
carnivoresand
andininmany
manymarine
marine
ecosystems
they
among
the
top
predators
(Bowen,
1997;
ecosystems
ecosystemsthey
theyareare
areamong
amongthe
thetop
toppredators
predators(Bowen,
(Bowen,1997;
1997;
Trites,
2002).
Their
diet
includes
a
wide
variety
of
prey
Trites,
Trites,2002).
2002).Their
Theirdiet
dietincludes
includesa awide
widevariety
varietyofofprey
prey
species
from
small
crustaceans
large
squid
(Barros
and
species
speciesfrom
fromsmall
smallcrustaceans
crustaceansupup
uptoto
tolarge
largesquid
squid(Barros
(Barrosand
and
Clarke,
2002).
They
have
a
few
predators
of
their
own;
these
Clarke,
They
ofoftheir
own;
Clarke,2002).
2002).
Theyhave
havea few
a fewpredators
predators
their
own;these
these
include
large
sharks,
aa small
number
other
cetaceans
and
include
includelarge
largesharks,
sharks,a small
smallnumber
numberofof
ofother
othercetaceans
cetaceansand
and
humans.
Given
their
large
body
sizes
and
relatively
high
humans.
humans.Given
Giventheir
theirlarge
largebody
bodysizes
sizesand
andrelatively
relativelyhigh
high
metabolic
rates,
cetaceans
can
represent
significant
metabolic
metabolic rates,
rates, cetaceans
cetaceans can
can represent
represent significant
significant
consumers
in
marine
ecosystems.
consumers
consumersininmarine
marineecosystems.
ecosystems.
Concerns
about
interactions
fisheries
with
marine
Concerns
Concernsabout
aboutthethe
theinteractions
interactionsofof
offisheries
fisherieswith
withmarine
marine
mammals
in
the
Mediterranean
Sea
are
probably
as
old
mammals
mammalsininthetheMediterranean
MediterraneanSea
Seaareareprobably
probablyasasold
oldasas
asthethe
the
first
human
attempts
catch
fish
with
aa net
(Bearzi,
2002).
first
firsthuman
humanattempts
attemptstoto
tocatch
catchfish
fishwith
witha net
net(Bearzi,
(Bearzi,2002).
2002).InIn
In
Mediterranean,
most
commercial
fish
stocks
considered
thethe
theMediterranean,
Mediterranean,most
mostcommercial
commercialfish
fishstocks
stocksareare
areconsidered
considered
overexploited
(Farrugio
1993).
This
adds
some
degree
overexploited
This
overexploited(Farrugio
(Farrugioetet
etal.,al.,
al.,1993).
1993).
Thisadds
addssome
somedegree
degreeofof
of
urgency
to
a
need
for
estimates
of
cetacean
consumption.
urgency
urgencytotoa aneed
needforforestimates
estimatesofofcetacean
cetaceanconsumption.
consumption.
Cetaceans
may
affected
fisheries
even
when
their
prey
Cetaceans
Cetaceansmay
maybebe
beaffected
affectedbyby
byfisheries
fisherieseven
evenwhen
whentheir
theirprey
prey
species
are
not
target
species
of
commercial
fisheries
because
species
areare
not
target
species
ofof
commercial
fisheries
because
ofof
species
not
target
species
commercial
fisheries
because
of
linkages
though
the
food
web
(Trites
et
al.,
1997).
In
addition,
linkages
linkagesthough
thoughthethefood
foodweb
web(Trites
(Tritesetetal.,al.,1997).
1997).InInaddition,
addition,
since
2002,
Ligurian
Sea,
located
northwestern
since
since2002,
2002,thethe
theLigurian
LigurianSea,
Sea,located
locatedinin
inthethe
thenorthwestern
northwestern
Mediterranean
Sea,
has
been
designated
aa Marine
Protected
Mediterranean
MediterraneanSea,
Sea,has
hasbeen
beendesignated
designatedasas
asa Marine
MarineProtected
Protected
Area
(MPA),
called
the
Pelagos
Sanctuary
(Fig.
1).
Area
Area(MPA),
(MPA),called
calledthethePelagos
PelagosSanctuary
Sanctuary(Fig.
(Fig.1).1).
summer,
Ligurian
Sea
attracts
large
numbers
InIn
Insummer,
summer,thethe
theLigurian
LigurianSea
Seaattracts
attractslarge
largenumbers
numbersofof
of
cetaceans
(Forcada
et
al.,
1996;
Forcada
and
Hammond,
cetaceans
cetaceans(Forcada
(Forcadaetetal.,
al.,1996;
1996;Forcada
Forcadaand
andHammond,
Hammond,
1998;
Gannier,
2005),
particular
striped
dolphins
(Stenella
1998;
1998;Gannier,
Gannier,2005),
2005),inin
inparticular
particularstriped
stripeddolphins
dolphins(Stenella
(Stenella
coeruleoalba)
and
fin
whales
(Balaenoptera
physalus).
coeruleoalba)
coeruleoalba)and
andfinfinwhales
whales(Balaenoptera
(Balaenopteraphysalus).
physalus).InIn
In
addition,
other
species
known
inhabit
this
area:
addition,
addition,sixsix
sixother
otherspecies
speciesareare
areknown
knowntoto
toinhabit
inhabitthis
thisarea:
area:
sperm
whales
(Physeter
macrocephalus);
Cuvier’s
beaked
sperm
spermwhales
whales(Physeter
(Physetermacrocephalus);
macrocephalus);Cuvier’s
Cuvier’sbeaked
beaked
whales
(Ziphius
cavirostris);
long-finned
pilot
whales
whales
whales (Ziphius
(Ziphius cavirostris);
cavirostris); long-finned
long-finned pilot
pilot whales
whales
(Globicephala
melas);
Risso’s
dolphins
(Grampus
griseus);
(Globicephala
(Globicephalamelas);
melas);Risso’s
Risso’sdolphins
dolphins(Grampus
(Grampusgriseus);
griseus);
bottlenose
dolphins
(Tursiops
truncatus);
and
more
rarely
bottlenose
bottlenosedolphins
dolphins(Tursiops
(Tursiopstruncatus);
truncatus);and
andmore
morerarely
rarely
short-beaked
common
dolphins
(Delphinus
delphis).
Summer
short-beaked
common
dolphins
(Delphinus
delphis).
Summer
short-beaked
common
dolphins
(Delphinus
delphis).
Summer
densities
have
previously
been
reported
striped
dolphins
densities
densitieshave
havepreviously
previouslybeen
beenreported
reportedforfor
forstriped
stripeddolphins
dolphins
(Forcada
and
Hammond,
1998;
Gannier,
1998)
and
whales
(Forcada
and
Hammond,
1998;
Gannier,
1998)
and
finfin
whales
(Forcada
and
Hammond,
1998;
Gannier,
1998)
and
fin
whales
(Forcada
et
al.,
1996;
Gannier,
1997),
however
those
for
other
(Forcada
etet
al.,
1996;
Gannier,
1997),
however
those
forfor
other
(Forcada
al.,
1996;
Gannier,
1997),
however
those
other
species
and
seasons
have
not
been
published
yet.
species
speciesand
andseasons
seasonshave
havenot
notbeen
beenpublished
publishedyet.
yet.
For
the
Mediterranean
Sea,
the
only
previous
estimates
For
Forthe
theMediterranean
MediterraneanSea,
Sea,the
theonly
onlyprevious
previousestimates
estimatesofof
of
cetacean
prey
consumption
were
Viale
(1985).
This
cetacean
cetaceanprey
preyconsumption
consumptionwere
werebyby
byViale
Viale(1985).
(1985).This
This
author
estimated
roughly
the
number
individuals
author
authorestimated
estimatedroughly
roughlythe
thenumber
numberofof
ofindividuals
individualsforfor
for
north
of
40°N
latitude
from
opportunistic
surveys
conducted
north
northofof40°N
40°Nlatitude
latitudefrom
fromopportunistic
opportunisticsurveys
surveysconducted
conducted
oceanographic
vessels
between
1972
and
1982.
was
onon
onoceanographic
oceanographicvessels
vesselsbetween
between1972
1972and
and1982.
1982.It It
Itwas
was
assumed
that
strip
transect
methodology
could
assumed
assumed that
that strip
strip transect
transect methodology
methodology could
could bebe
be
considered
and
the
effective
strip
half-width
used
was
taken
considered
consideredand
andthe
theeffective
effectivestrip
striphalf-width
half-widthused
usedwas
wastaken
taken
from
other
studies.
With
additional
survey
data
allow
from
fromother
otherstudies.
studies.With
Withadditional
additionalsurvey
surveydata
datatoto
toallow
allow
estimation
of
cetacean
densities
throughout
the
year,
better
estimation
year,
better
estimationofof
ofcetacean
cetaceandensities
densitiesthroughout
throughoutthe
the
year,
better
estimation
cetacean
densities
throughout
the
year,
accurate
estimates
consumption
rates
now
possible.
estimates
estimatesofof
ofconsumption
consumptionrates
ratesareare
arenow
nowpossible.
possible.
A
single-species
approach
to
estimating
consumption
rates
AA
single-species
approach
toto
estimating
consumption
rates
single-species
approach
estimating
consumption
rates
or
trophic
relationships
beginning
from
population
size
has
orortrophic
trophicrelationships
relationshipsbeginning
beginningfrom
frompopulation
populationsize
sizehas
hasa aa
number
limitations
when
dealing
with
multiple
species,
number
numberofof
oflimitations
limitationswhen
whendealing
dealingwith
withmultiple
multiplespecies,
species,
especially
terms
ecological
requirements
species
that
especially
especiallyinin
interms
termsofof
ofecological
ecologicalrequirements
requirementsofof
ofspecies
speciesthat
that
vary
widely
in
body
size.
In
this
paper,
an
attempt
was
made
vary
varywidely
widelyininbody
bodysize.
size.InInthis
thispaper,
paper,ananattempt
attemptwas
wasmade
made
estimate
annual
prey
consumption
rates
cetaceans
toto
toestimate
estimateannual
annualprey
preyconsumption
consumptionrates
ratesbyby
bycetaceans
cetaceansinin
in
the
Ligurian
Sea,
and
their
overall
trophic
impacts
thetheLigurian
LigurianSea,
Sea,and
andtheir
theiroverall
overalltrophic
trophicimpacts
impactsasas
as
measured
primary
production
required
support
that
measured
measuredbyby
byprimary
primaryproduction
productionrequired
requiredtoto
tosupport
supportthat
that
consumption.
It
has
been
assumed
that
cetaceans
use
consumption.
consumption.It Ithas
hasbeen
beenassumed
assumedthat
thatcetaceans
cetaceansuse
usethethe
the
habitat
feeding
purposes,
majority
species,
habitat
habitatforfor
forfeeding
feedingpurposes,
purposes,asas
asforfor
forthethe
themajority
majorityofof
ofspecies,
species,
feeding
activity
was
observed
acoustically
verified
several
feeding
activity
was
observed
oror
acoustically
verified
several
feeding
activity
was
observed
or
acoustically
verified
several
times
during
surveys,
except
pilot
whales,
which
times
timesduring
duringsurveys,
surveys,except
exceptforfor
forpilot
pilotwhales,
whales,which
whichareare
are
known
feed
night
(Baird
al.,
2002).
known
knowntoto
tofeed
feedatat
atnight
night(Baird
(Bairdetet
etal.,
al.,2002).
2002).
* Centre de Recherche sur les Cétacés, Marineland-Parques Reunidos, 306 av Mozart, 06600 Antibes, France.
* Centre
dede
Recherche
sursur
lesles
Cétacés,
Marineland-Parques
Reunidos,
306
avav
Mozart,
06600
Antibes,
France.
* Centre
Recherche
Cétacés,
Marineland-Parques
Reunidos,
306
Mozart,
06600
Antibes,
France.
+ Laboratory for Polar Ecology (PolE), rue du Fodia 18, B-1367 Ramillies, Belgium.
++
Laboratory
forfor
Polar
Ecology
(PolE),
ruerue
dudu
Fodia
18,18,
B-1367
Ramillies,
Belgium.
Laboratory
Polar
Ecology
(PolE),
Fodia
B-1367
Ramillies,
Belgium.
# Groupe de Recherche sur les Cétacés, BP 715, 06633 Antibes, France.
# Groupe
dede
Recherche
sursur
lesles
Cétacés,
BPBP
715,
06633
Antibes,
France.
# Groupe
Recherche
Cétacés,
715,
06633
Antibes,
France.
^ Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882, USA.
^ Graduate
School
of of
Oceanography,
University
of of
Rhode
Island,
Narragansett,
Rhode
Island
02882,
USA.
^ Graduate
School
Oceanography,
University
Rhode
Island,
Narragansett,
Rhode
Island
02882,
USA.
32
32
32
LARAN et
et
al.:
SEASONAL
ESTIMATES
OF
CETACEANS
IN
THE
LIGURUIAN
SEA
LARAN et al.:
al.: SEASONAL
SEASONAL ESTIMATES
ESTIMATES OF
OF CETACEANS
CETACEANS IN
IN THE
THE LIGURUIAN
LIGURIAN SEA
LARAN
al.:
SEASONAL
ESTIMATES
OF
CETACEANS
IN
THE
LIGURUIAN
LARAN
et
SEA
Fig. 1.
1. Study
Study area
area with
with transect
transect locations
locations (black
(black and
and grey
grey lines),
lines), PELAGOS
PELAGOS Sanctuary
Sanctuary borders
borders (dashed
(dashed lines)
lines) and
and Sardinia
Sardinia area
area (FAO).
(FAO).
Fig.
Fig.
1. Study
area with
transect locations
(black and
grey lines),
PELAGOS Sanctuary
borders (dashed
lines) and
Sardinia area
(FAO).
MATERIALS AND
AND METHODS
METHODS
MATERIALS
MATERIALS
AND METHODS
The Ligurian
Ligurian Sea
Sea is
is located
located north
north of
of the
the western
western
The
The
Ligurian Sea
is located
north of
the western
Mediterranean basin
basin (Fig.
(Fig. 1).
1). This
This region
region includes
includes large
large areas
areas
Mediterranean
Mediterranean basin (Fig. 1). This region includes large areas
of deep
deep water
water (>2,000m),
(>2,000m), with
with aa narrow
narrow continental
continental shelf.
shelf. It
It
of
of deep water (>2,000m), with a narrow continental shelf. It
is characterised
characterised by
by aa frontal
frontal system,
system, which
which provides
provides aa high
high
is
is characterised by a frontal system, which provides a high
level of
of primary
primary production,
production, peaking
peaking in
in March-April
March-April (Jacques
(Jacques
level
level
of primary
production, peaking
in March-April
(Jacques
et al.,
al., 1973;
1973; Nival
Nival et
et al.,
al., 1975).
1975). The
The Pelagos
Pelagos Sanctuary
Sanctuary
et
et al., 1973; Nival2 et al., 1975). The Pelagos Sanctuary
includes 87,500km
87,500km2, but
but the
the estimates
estimates used
used in
in this
this study
study only
only
includes
includes
87,500km2,, but
the estimates
used in
this study
only
pertain to
to the
the northernmost
northernmost portion
portion (Fig.
(Fig. 1).
1). In
In the
the absence
absence of
of
pertain
pertain to the northernmost portion (Fig. 1). In the absence of
seasonal
surveys
of
the
whole
MPA,
cetacean
density
was
seasonal surveys
surveys of
of the
the whole
whole MPA,
MPA, cetacean
cetacean density
density was
was
seasonal
estimated from
from transects
transects conducted
conducted only
only in
in its
its northern
northern part.
part.
estimated
estimated
from transects
conducted only
in its
northern part.
It must
must be
be noted
noted that
that environmental
environmental conditions
conditions in
in the
the corridor
corridor
It
It
must be
noted that
environmental conditions
in the
corridor
do not
not represent
represent those
those of
of the
the entire
entire MPA
MPA and
and that
that some
some
do
do not represent those of the entire MPA and that some
cetaceans
(e.g.
fin
whales)
are
known
to
aggregate
near
the
cetaceans (e.g.
(e.g. fin
fin whales)
whales) are
are known
known to
to aggregate
aggregate near
near the
the
cetaceans
northern frontal
frontal region
region in
in summer.
summer. Nevertheless
Nevertheless it
it was
was
northern
northern frontal region in summer. Nevertheless it was
considered that
that even
even rough
rough estimates
estimates of
of biomass,
biomass, densities
densities
considered
considered
that even
rough estimates
of biomass,
densities
and predation
predation could
could be
be useful
useful in
in term
term of
of management.
management. For
For all
all
and
and predation could be useful in term of management. For all
estimates,
the
year
was
divided
into
two
equal
periods,
Aprilestimates, the
the year
year was
was divided
divided into
into two
two equal
equal periods,
periods, AprilAprilestimates,
September and
and October-March,
October-March, which
which are
are referred
referred to
to as
as
September
September
and October-March,
which are
referred to
as
‘summer’ and
and ‘winter’
‘winter’ respectively,
respectively, for
for convenience.
convenience.
‘summer’
‘summer’ and ‘winter’ respectively, for convenience.
Density estimates
estimates
Density
Density
estimates
Data were
were collected
collected between
between February
February 2001
2001 and
and February
February
Data
Data were collected between
February 2001
and February
2004 from
from 30
30 dedicated
dedicated line-transect
line-transect surveys,
surveys, conducted
conducted
2004
2004 from 30 dedicated line-transect surveys, conducted
monthly along
along the
the same
same 160km
160km track
track between
between the
the French
French
monthly
monthly
along the
same 160km
track between
the French
mainland
and
Corsica
(Fig.
1)
and
part
of
the
return
transect.
mainland and
and Corsica
Corsica (Fig.
(Fig. 1)
1) and
and part
part of
of the
the return
return transect.
transect.
mainland
The standard
standard sampling
sampling design
design was
was to
to survey
survey from
from France
France to
to
The
The
standard sampling
design was
to survey
from
France
to
-1 (12knots). In this
-1
Corsica at
at aa speed
speed of
of about
about 22km
22km hh-1
(12knots).
In
this
Corsica
this
Corsica at a speed of about 22km h (12knots).
-1 andIn23km
-1
analysis only
only effort
effort conducted
conducted between
between 18km
18km-1hh-1
analysis
and
23km
analysis
onlyeffort
effortconducted
conductedbetween
between18km
18km
23km
analysis
only
h handand
23km
h-1
-1
-1 under
h-1
under sea
sea conditions
conditions of
of Beaufort
Beaufort 33 or
or lower
lower was
was
h
h under
conditionsof ofBeaufort
Beaufort3 3 oror lower
lower was
was
under
sea sea
conditions
considered. The
The return
return trip
trip on
on the
the next
next day
day followed
followed aa
considered.
considered.
The return
trip on
the next
day followed
a
parallel transect
transect offset
offset 11km
11km north-east
north-east from
from the
the southbound
southbound
parallel
parallel
transect offset
11km north-east
from the
southbound
track. A
A shorter
shorter (74km)
(74km) section
section of
of the
the northbound
northbound transect
transect
track.
track.
A shorter
(74km) section
of the
northbound transect
-1
-1
was
surveyed
at
lower
speeds
(13km
h
)
to
try
to
estimate
was surveyed
surveyed at
at lower
lower speeds
speeds (13km
(13km hh-1)) to
to try
try to
to estimate
estimate
was
the probability
probability of
of seeing
seeing a whale
whale on
on the
the trackline,
trackline, g(0),
g(0), for
for
the
the
probability of
seeing aa whale
on the
trackline, g(0),
for
the most
most common
common species.
species. Only
Only sections
sections of
of the
the northbound
northbound
the
the most common species. Only sections
of the northbound
-1, before
transect conducted
conducted at
at 18-23km
18-23km h-1
and after
after the
the
transect
before and
and
transect
conducted at
18-23km hh-1,, before
after the
lower-speed
segment,
were
included
in
the
analysis.
There
lower-speed segment,
segment, were
were included
included in
in the
the analysis.
analysis. There
There
lower-speed
was one
one additional
additional survey
survey conducted
conducted in
in summer
summer 2001
2001
was
was
one additional
survey conducted
in summer
2001
within the
the same
same general
general area
area in
in the
the sanctuary
sanctuary (Gannier,
(Gannier,
within
within
the same
general area
in the
sanctuary (Gannier,
2006) (Fig.
(Fig. 1).
1). All
All surveys
surveys were
were conducted
conducted with
with the
the same
same
2006)
2006) (Fig. 1). All surveys were conducted with the same
dedicated platform,
platform, aa 13m
13m vessel
vessel powered
powered by
by two
two 350HP
350HP
dedicated
dedicated platform, a 13m vessel powered by two 350HP
inboard engines,
engines, and
and aa consistent
consistent crew.
crew. Three
Three experienced
experienced
inboard
inboard
engines, and
a consistent crew.
Three experienced
observers,
seated
with
their
eyes
4m
above
the water
water
observers, seated
seated with
with their
their eyes
eyes 4m
4m above
above the
the
observers,
water
surface, searched
searched the
the forward
forward sector
sector (-90°
(-90° to
to +90°
+90° relative
relative to
to
surface,
surface, searched the forward sector (-90° to +90° relative to
the bow)
bow) with
with the
the naked
naked eye
eye and
and were
were rotated
rotated every
every hour
hour
the
the bow) with the naked eye and were rotated every hour
(see Laran
Laran and
and Drouot-Dulau,
Drouot-Dulau, 2007).
2007).
(see
(see
Laran and
Drouot-Dulau, 2007).
The
survey
data
were
grouped
by six-month
six-month seasons
seasons
The survey
survey data
data were
were grouped
grouped by
by
The
six-month seasons
across the
the three
three years
years of
of sampling
sampling and
and analysed
analysed applying
applying
across
across the three years of sampling and analysed applying
standard line-transect
line-transect methods
methods (Buckland
(Buckland et
et al.,
al., 2001).
2001).
standard
standard
line-transect methods
(Buckland et
al., 2001).
Transects
selected
for
analysis
varied
from
10
to
158km
Transects selected
selected for
for analysis
analysis varied
varied from
from 10
10 to
to 158km
158km
Transects
(mean=81.7km) depending
depending the
the length
length of
of segment
segment conducted
conducted
(mean=81.7km)
(mean=81.7km)
depending the
length of
segment conducted
with good
good sighting
sighting conditions.
conditions. The
The effective
effective strip
strip half-width
half-width
with
with
good sighting
conditions. The
effective strip
half-width
(esw) was
was estimated
estimated for
for each
each species
species using
using Distance
Distance 5.0
5.0
(esw)
(esw) was estimated for each species using Distance 5.0
(Thomas
et
al.,
2006);
as
the
numbers
of
sightings
were
too
(Thomas et
et al.,
al., 2006);
2006); as
as the
the numbers
numbers of
of sightings
sightings were
were too
too
(Thomas
low to
to reliably
reliably estimate
estimate esw
esw for
for Risso’s
Risso’s dolphins
dolphins and
and pilot
pilot
low
low
to reliably
estimate esw
for Risso’s
dolphins and
pilot
whales, additional
additional detections
detections of
of the
the same
same species,
species, recorded
recorded
whales,
whales,
additional detections
of the
same species,
recorded
in the
the northwestern
northwestern Mediterranean
Mediterranean Sea
Sea from
from the
the same
same
in
in the northwestern Mediterranean Sea from the same
platform
were
included.
For
fin
whales
and
striped
dolphins,
platform were
were included.
included. For
For fin
fin whales
whales and
and striped
striped dolphins,
dolphins,
platform
sightings were
were truncated
truncated prior
prior to
to analysis
analysis to
to exclude
exclude 5%
5% of
of
sightings
sightings
were truncated
prior to
analysis to
exclude 5%
of
the groups
groups detected
detected at
at the
the largest
largest distances
distances following
following
the
the groups detected at the largest distances following
Buckland et
et al.
al. (2001).
(2001). The
The density
density of
of species
species ii during
during
Buckland
Buckland
et al.
(2001). The
of species
i during
2density
2
)
was
estimated
by:
period
j
(in
individuals
per
km
was estimated
estimated by:
by:
period jj (in
(in individuals
individuals per
per km
km2)) was
period
(1)
(1)
(1)
where ssijij is
is the
the mean
mean school
school size
size of
of species
species i during
during period
period j;
j;
where
where
s is the
mean school
size of
species ii during
period j;
nijij is
is the
theij number
number of
of primary
primary sightings
sightings (after
(after truncation)
truncation) of
of
n
nij is the number of primary sightings (after truncation) of
species ii during
during period
period jj and
and L
Ljj is
is the
the total
total transect
transect length
length (km)
(km)
species
species
i during period
j and L
the total
transect length
(km)
j isvariance
surveyed
during
period
j.
The
of
D
was
estimated
surveyed during
during period
period j.j. The
The variance
variance of
of D
D was
was estimated
estimated
surveyed
using Distance
Distance 5.0,
5.0, by
by the
the delta
delta method
method (Buckland
(Buckland et
et al.,
al.,
using
using
Distance 5.0,
by the
delta method
(Buckland et
al.,
2001). Replicate
Replicate transects
transects weighted
weighted by
by transect
transect length
length were
were
2001).
2001). Replicate transects weighted by transect length were
considered to
to estimate
estimate var(n).
var(n).
The annual
annual variance
variance or
or groups
groups
nn The
considered
The
considered
to estimate
var(n).
annual variance
or groups
of
species
variances
were
estimated
as
the
sum
of
variances
of
of species
species variances
variances were
were estimated
estimated as
as the
the sum
sum of
of variances
variances of
of
of
the
different
components
(Buckland
et
al.,
2001).
the different
different components
components (Buckland
(Buckland et
et al.,
al., 2001).
2001).
the
For sperm
sperm whales,
whales, aa strip-transect
strip-transect method
method was
was applied
applied to
to
For
For
sperm whales,
a strip-transect method
was applied
to
combined visual
visual and
and acoustic
acoustic detections.
detections. Two-minute
Two-minute
combined
combined visual and acoustic detections. Two-minute
recording sessions
sessions (with
(with the
the vessel
vessel propeller
propeller de-clutched)
de-clutched)
recording
recording
sessions (with
the vessel
propeller de-clutched)
J. CETACEAN RES. MANAGE. 11(1):31–40, 2009
33
MANAGE. 11(1):31–­­
11(1):31–40,
2009
33
J. CETACEAN
CETACEAN RES. MANAGE.
40, 2010
CETACEAN
RES. MANAGE.
11(1):31–40,
2009 modified that model by adjusting the
33
were performed, each 18.5km of the J.
southbound
transect,
Kenney
et al. (1997)
were aperformed,
each 18.5km(Magrec,
of the southbound
with
monaural hydrophone
HP 60MT).transect,
As the
were aperformed,
each
18.5km(Magrec,
of the southbound
transect,
with
monaural
hydrophone
HP 60MT).
As the
exact
number
of
whales
could
not
be
reliably
determined
with anumber
monaural
hydrophone
(Magrec,
HP 60MT).
As the
exact
of
whales
could
not
be
reliably
determined
when
more
thanofthree
whales
were
vocally
active determined
in the area,
exact
number
whales
could
not
be
reliably
when was
morethe
thanmaximum
three whales
weresize
vocally
activeby
in the
area,
three
school
allocated
acoustic
when more
thanmaximum
three whales
weresize
vocally
activeby
in the
area,
three
was alone
the
school
allocated
acoustic
sampling
(Gannier
et
al.,
2002).
Two
consecutive
three
was
the
maximum
school
size
allocated
by
acoustic
samplingstations
alone or
(Gannier
et al.,
2002).
Two consecutivea
positive
a positive
station
following/preceding
samplingstations
alone or
(Gannier
et al.,
2002).
Two consecutive
positive
a
positive
station
following/preceding
sighting
were considered
asstation
distinct
whales when theaa
positive
stations
or
a
positive
following/preceding
sighting click-level
were considered
as equal
distinct
whalesthan
when
recorded
index was
or greater
3 (onthe
a
sighting click-level
were considered
as equal
distinct
whalesthan
when
recorded
index
was
or greater
3 (onthea
scale
varying
from
0
to
5;
see
Laran
and
Drouot-Dulau,
recorded
click-level
index
wassee
equal or greater
than 3 (on a
scale
varying
fromwhales
0 to 5;
andproduce
Drouot-Dulau,
2007).
As sperm
dosee
notLaran
usually
regular
scale
varying
from
0
to
5;
Laran
and
Drouot-Dulau,
2007).atAs
sperm
whales
doet not
usually
produce
regular
clicks
the
surface
(Drouot
al.,
2004),
the
school
size of
2007).atAs
whales
doetnot
usually
produce
regular
clicks
thesperm
surface
(Drouot
al.,
2004),
the
school
sizeand
of
each
sighting
was
estimated
by
combining
visual
clicks
at
the
surface
(Drouot
et
al.,
2004),
the
school
sizeand
of
each sighting
was estimated
by combining
visual
acoustic
information.
With
the
same
monaural
hydrophone,
each
sighting
was
estimated
by
combining
visual
and
acoustic et
information.
With the asame
monaural
hydrophone,
Gannier
al. (2002) observed
click-level
index
of 0 for a
acoustic et
information.
With the asame
monaural
hydrophone,
Gannier
al.
(2002)
observed
click-level
index
of 9.4km;
0 for a
sperm
whale
located
at
14.8km
and
a
level
of
2
at
Gannierwhale
et al.located
(2002) observed
click-level
of 9.4km;
0 for a
sperm
atestimated
14.8kma and
awhales
levelindex
of
2 at
from
their
results
it
is
that
were
heard
up
sperm
whale
located
at
14.8km
and
a
level
of
2
at
9.4km;
from to
their
results
it (see
is estimated
that
whales
were heard up
from
13km
away
fig.
3,
plot
for
mono-hydrophone,
in
from
their
results
it (see
isfig.
estimated
that
were heard up
to 13km
away
(see
3, 3,
plot
for
mono-hydrophone,
in
from
to
13km
away
fig.
plot
forwhales
mono-hydrophone,
in
Gannier
et
al.
2002).
Therefore
an
arbitrary
distance
of
13km
from to 13km
away (see
fig. 3, plot
for mono-hydrophone,
in
Gannier
et
al.
2002).
Therefore
an
arbitrary
distance
of
13km
was
assumed
to
be acoustically
scanned
ondistance
each side
of
the
Gannier
et
al.
2002).
Therefore
an
arbitrary
of
13km
was assumed
to be acoustically
on each
of the
transect
line (equivalent
to esw),scanned
considering
theside
detection
was assumed
to be acoustically
scanned
on each
side
of the
transect
line
(equivalent
to esw),
considering
the
detection
capability
of
the
hydrophone.
The
calculation
of
sperm
whale
transect
line
(equivalent
to
esw),
considering
the
detection
capability
ofequivalent
the hydrophone.
of sperm whale
density
was
to Eqn.The
(1).calculation
capability
ofequivalent
the hydrophone.
density
was
to Eqn.The
(1).calculation of sperm whale
density was equivalent to Eqn. (1).
Biomass and prey consumption
Biomass and
prey consumption
Biomass
densities
for each species were estimated by
Biomass and
prey consumption
Biomass
densities
fordensities
each species
were
estimated
multiplying
calculated
by average
body
mass (Wby
in
Biomass densities
fordensities
each species
were
estimated
multiplying
calculated
by
average
body
mass
(Wby
in
kg).
The
mean
body
mass
values,
for
males
and
females
multiplying
calculated
densities
by average
bodyand
mass
(W in
kg).
The mean
body
mass
values,
forPauly
males
females
separately,
were
taken
from
Trites
and
(1998)
except
kg). The mean
body
mass
forPauly
males(1998)
and females
separately,
taken
from values,
Tritesevidence
and
except
for
specieswere
where
independent
suggested
that
separately,
were
taken
from
Trites
and
Pauly
(1998)
except
for species inwhere
independent tended
evidence
suggested
that
individuals
the
Mediterranean
to
be
smaller
than
for species inwhere
independent tended
evidence
suggested
that
individuals
the
Mediterranean
to
be
smaller
than
elsewhere
ininthe
world.
In those tended
cases, to
maximum
lengths
individuals
the
Mediterranean
be
smaller
than
elsewhere
in the world. were
In those
lengths
from
the Mediterranean
used cases,
in the maximum
regression models
elsewhere
in the world. were
In those
cases,
lengths
from
the Mediterranean
used
in the maximum
regression
models
from
Trites
and
Pauly
(1998)
to
compute
mean
weights
for
from
the
Mediterranean
were
used
in
the
regression
models
from Trites
andfemales.
Pauly (1998)
to compute
meanlengths
weights
for
males
and
Maximum
body
for
from Trites
andfemales.
Pauly (1998)
to compute
meanlengths
weights for
for
males
and
Maximum
body
Mediterranean
specimensMaximum
came from
thelengths
long-term
males
and
females.
body
for
Mediterranean
specimens
from bytheF. Dhermain
long-term
stranding
database
and werecame
provided
Mediterranean
specimens
from bytheF. Dhermain
long-term
stranding
database
and
werecame
provided
(Groupe
d’Etude
des
Cétacés
de
Méditerranée)
and
O. Van
stranding
database
and
were
provided
by
F.
Dhermain
(Groupe (Centre
d’Etude
desRecherche
Cétacés
de
Méditerranée)
andMarins).
O. Van
(Groupe
d’Etude
des
Cétacés
de Mammifères
Méditerranée)
and
Canneyt
de
sur
les
(Groupe
d’Etudede
des
Cétacés
de
Méditerranée)
and
O. Van
Canneyt
(Centre
Recherche
sur
les
Mammifères
Marins).
O.
Van
Canneyt
(CRMM
University
of
La
Rochelle).
For
each (Centre
species de
theRecherche
male and female
means were averaged
Canneyt
sur les Mammifères
Marins).
For
each
species
male to
andbefemale
meansfor
were
with
the sex
ratio the
assumed
50%, except
theaveraged
strongly
For
each
species
the
male
and
female
means
were
averaged
with the sexspecies
ratio assumed
to be 50%,
except
for thewhere
strongly
dimorphic
(sperm
whale
and
pilot
whale),
the
with the sexspecies
ratio assumed
to be 50%,
except
for thewhere
strongly
dimorphic
(spermtowhale
and male
pilot
whale),
the
sex
ratio
was
assumed
be
40%
and
60%
female
dimorphic
species
(spermtowhale
and male
pilot whale),
where
the
sex
ratio
was
assumed
be
40%
and
60%
female
(following
Barlow
et al.,to
2008;
Tritesmale
and Pauly,
1998).
The
sex
ratio
was
assumed
be
40%
and
60%
female
(following
Barlow etdensity
al., 2008;
Triteswas
andassumed
Pauly, 1998).
CV
of the biomass
estimate
to beThe
the
(following
Barlow etdensity
al., 2008;
Triteswas
andassumed
Pauly, 1998).
CV
ofasthe
biomass
estimate
to beThe
the
same
that
of
the
corresponding
density,
as
no
information
CV ofasthe
biomass
density estimate
was assumed
to be the
same
that
oflength
the corresponding
density,
as no information
on
maximum
variability
was
available.
Cumulative
same
as that oflength
the corresponding
density,
as no information
on
maximum
was
available.
biomass
densities
forvariability
all odontocetes
and totalCumulative
cetaceans
on
maximum
length
variability
was
available.
Cumulative
biomass
densities
for all odontocetes
andfortotal
cetaceans
were
computed
by summing
the estimates
the individual
biomass
densities
for
all
odontocetes
and
total
cetaceans
were computed
by summing
thewere
estimates
for the
individual
species,
and
cumulative
CV’s
computed
by
summing
were
computed
by
summing
the
estimates
for
the
individual
species,
and cumulative
CV’s wereBuckland
computedetby
summing
the
individual
variances
(following
al.,
2001).
species,
and cumulative
CV’s wereBuckland
computedetbyal.,summing
the
individual
variances
(following
2001).
A
variety
of
methods
exist
for
estimating
the
consumption
theAindividual
(following
Buckland
etconsumption
al., 2001).
variety
of variances
methods
exist
for
estimating
the
rates
of
cetaceans
(see
review
by
Leaper
and
Lavigne,
2007).
A variety
of methods
exist for
estimating
consumption
rates
of cetaceans
(see review
by
Leaper
andthe
Lavigne,
2007).
Sergeant
(1969),
extrapolating
from
feeding
rates
of
captive
rates of cetaceans
(see review byfrom
Leaper
and Lavigne,
2007).
Sergeant
(1969),
extrapolating
feeding
rates oftocaptive
odontocetes
ranging
in
size
from
harbour
porpoises
killer
Sergeant
(1969),
extrapolating
from
feeding
rates
of
captive
odontocetes
ranging
infeeding
size from
harbour
porpoisescetaceans
to killer
whales,
proposed
that
rates
of
free-living
odontocetes
ranging infeeding
size from
harbour
porpoisescetaceans
to killer
whales,
rates
of body
free-living
could
beproposed
computedthat
as afeeding
percentage
of
weight,cetaceans
ranging
whales,
proposed
that
rates
of
free-living
could 3.5-4%
be computed
as a animals
percentage
of body weight,
ranging
from
in
larger
to
10-12%
in
the
smallest
could 3.5-4%
be computed
as a animals
percentage
of body weight,
ranging
from
in he
larger
tomathematical
10-12%
in the
smallest
individuals,
but
did
not
fit
a
model.
The
from
3.5-4%
in
larger
animals
to
10-12%
in
the
smallest
individuals,
but he did models
not fit aaremathematical
model.
The
available
mathematical
generally
of
two
types:
individuals,
but he did models
not fit aare
mathematical
The
available
mathematical
generally
ofmodel.
two
types:
computing
ingestion
rate
as
a
function
of
body
weight;
or
available
mathematical
models
are
generally
of
two
types:
computing metabolic
ingestion rate
as
a function
function of
of body
body weight
weight;and
or
computing
rate
as
a
computing metabolic
ingestion rate
function of
of body
body weight
weight;and
or
computing
rate as
as rate
aa function
scaling
upward
to
ingestion
for
assimilation
efficiency
computing
metabolic
rate
as
a
function
of
body
weight
and
scaling
upward
to etingestion
rate
for assimilation
and
activity.
Innes
al. (1987)
proposed
that daily efficiency
ration (R,
scaling
upward
to et
ingestion
rate
for assimilation
efficiency
-1) could
and
activity.
Innes
al. (1987)
proposed
that daily
ration
(R,
be
estimated
from
body
weight
(W, in
kg) by:
in
kg
d
and
activity.
Innes
et
al.
(1987)
proposed
that
daily
ration
(R,
)
could
be
estimated
from
body
weight
(W,
in
kg)
by:
in kg d-1
in kg d-1R)1could
be estimated
from body weight (W, in kg) by:
= 0.123
W 0.8
(2)
R1 = 0.123 W 0.8
(2)
R1 = 0.123 W 0.8
(2)
Trites etetal.
modified
that
by
the
Kenney
al.(1997)
(1997)
modifiedin
that
model
bytoadjusting
adjusting
multiplier
downward
anmodel
attempt
account the
for
Kenney et slightly
al. (1997)
modifiedinthat
model
bytoadjusting
the
multiplier
slightly
downward
an
attempt
account
for
the
difference
between
ingestion
for
growth
and
ingestion
multiplier
slightly
downward
in an
attempt
toand
account
for
the
difference
between
ingestion
for
growth
ingestion
for
maintenance:
the
difference
between
ingestion
for
growth
and
ingestion
for maintenance:
for maintenance:
R2= 0.1 W 0.8
(3)
R2= 0.1 W 0.8
(3)
0.8
= 0.1
W used the model of Kleiber (1975) (3)
Trites etR2al.
(1997)
to
-1): (1975)
Kenney
(1997)used
used
the
modelinof
ofkcal
Kleiber
(1975) to
to
Trites etet
al.al.(1997)
the
model
Kleiber
estimate
basal
metabolic
rate
(BMR,
d
Trites et basal
al. (1997)
usedrate
the(BMR,
model inofkcal
Kleiber
(1975) to
estimate
metabolic
d-1
):
estimateBMR
basal= metabolic
70 W 0.75 rate (BMR, in kcal d-1):
(4)
BMR = 70 W 0.75
(4)
0.75
= 70a W
(4)
and thenBMR
applied
scaling factor to account for assimilation
and then applied
a scaling factor to account for assimilation
efficiency
and
activity:
and then applied
a scaling factor to account for assimilation
efficiency
and activity:
efficiency and activity:
(5)
(5)
(5)
where E is the energy density of the prey consumed,
-1 for
where E to
is be
the 1,000kcal
energy density
of fish
the prey
consumed,
assumed
kg
and
crustaceans
where E to
is be
the 1,000kcal
energy density
of fish
the prey
consumed,
-1 for
assumed
and
(Clarke
and
Prince,
1980; kg
Sissenwine
al., crustaceans
1984) and
-1 for fishet and
assumed
to
be
1,000kcal
kg
crustaceans
(Clarke and
1980; (Croxall
Sissenwine
al., 1984)
and
830kcal
kg-1Prince,
for squid
andet
Prince,
1982).
(Clarke and
Prince,
1980; (Croxall
Sissenwine
al., 1984)
and
830kcal
kg-1
forVíkingsson
squid
andetLockyer’s
Prince,
1982).
Sigurjónsson
and
(1997)
used
(1981)
-1
830kcal
kg
for
squid
(Croxall
and
Prince,
1982).
Sigurjónsson
and Víkingsson
Lockyer’s (1981)
model
for near-basal
metabolic(1997)
rate: used
Sigurjónsson
and Víkingsson
(1997)
model
for near-basal
metabolic
rate: used Lockyer’s (1981)
model for
metabolic rate:
M =near-basal
110 W 0.783
(6)
M = 110 W 0.783
(6)
0.783
= 110
(6)
which M
they
thenW scaled upwards for 80% assimilation
which theyand
then
scaledactivity
upwards
for 80%
assimilation
efficiency
a
1.5×
factor.
Incorporating
the
which theyand
then
scaledactivity
upwards
for 80% assimilation
efficiency
a 1.5×
factor.
the
energy-to-biomass
conversion,
their
modelIncorporating
becomes:
efficiency
and
a
1.5×
activity
factor.
the
energy-to-biomass conversion, their modelIncorporating
becomes:
energy-to-biomass conversion, their model becomes:
(7)
(7)
All four models were used to estimate the daily rations (7)
of
All four models
were
usedfrom
to estimate
the
daily
rations
of
cetaceans
ranging
in
size
30kg
to
100t
(i.e.
harbour
All four models
were
usedfrom
to estimate
daily
of
cetaceans
ranging
in
size
30kg tothe
100t
(i.e.rations
harbour
porpoise
to
blue
whale),
presuming
the
same
diet
at
cetaceans
ranging
in
size
from
30kg
to
100t
(i.e.
harbour
-1
porpoise to
blue
whale),
presuming
theand
same
diet at
1,000kcal
kg
(Fig.
2).
The
Sigurjónsson
Víkingsson
porpoise to
blue
whale),
presuming theand
same
diet at
(Fig.
2). in
The
Víkingsson
1,000kcal
kg-1
(1997)
method
resulted
theSigurjónsson
highest estimates
across the
-1 (Fig.
2).
The
Sigurjónsson
and
Víkingsson
1,000kcal
kg
(1997)range,
method
in the
highest
estimates
the
entire
andresulted
the Trites
et al.
(1997)
method across
generated
(1997)range,
method
in the
highest
estimates
across
the
entire
andresulted
the
Trites
et
al.
(1997)
method
generated
the
lowest
values
at
all
but
the
very
largest
body
weights.
entire
range,
and
the
Trites
et
al.
(1997)
method
generated
the lowest
values
at all and
but the
very et
largest
body methods
weights.
The
Innes et
al. (1987)
Kenney
al. (1997)
the lowest
values
at all and
but the
very et
largest
body methods
weights.
The
Innes intermediate
et
al. (1987)
Kenney
al.latter
(1997)
produced
values,
with
the
differing
in
The
Innes
et
al.
(1987)
and
Kenney
et
al.
(1997)
methods
produced
intermediate
values,
with
the latter
differing
in
slope.
Barlow
et
al.
(2008)
tested
an
even
broader
range
of
produced
intermediate
values,
with
the latter
differing
in
slope.
Barlow
et al. (2008)
tested
an the
even
broader
range
of
consumption
models,
and
settled
on
same
one
used
by
slope.
Barlow
et
al.
(2008)
tested
an
even
broader
range
of
consumption
settled
the samethat
onethe
used
by
Kenney
et al.models,
(1997).and
They
also on
concluded
same
consumption
models,
and
settled
on
the samethat
onethe
used
by
Kenney
et al.3.0
(1997).
They
also
concluded
same
model
using
as
a
multiplier
rather
than
2.5
(Fig.
2)
and
Kenney
et
al.
(1997).
They
also
concluded
that
the
same
model using 3.0 as a multiplier rather than 2.5 (Fig. 2) and
model using 3.0 as a multiplier rather than 2.5 (Fig. 2) and
Fig.
of daily
Fi
g. 2.
2. Estimates
Estimates of
daily ration
ration (as
(as aa percentage
percentage of
of body
body mass)
mass) from
from
Fig.
2.
Estimates
of
daily
ration
(as
a
percentage
of
body
mass)
from
body
mass
for
cetaceans
from
30kg
(e.g.
an
average
male
harbour
body
mass for cetaceans
from (as
30kg
(e.g. an average
male
harbour
Fig.
2.
Estimates
of
daily
ration
a
percentage
of
body
mass)
from
body massto
cetaceans
(e.g.
an average
male different
harbour
porpoise)
tofor
100
tonnes from
(e.g. 30kg
whale)
from
porpoise)
100
tonnes
(e.g.
aa blue
blue
whale)
from four
four
different
body mass
30kg
(e.g.
an average
male
harbour
porpoise)
tofor100
(e.g.
a blue
whale)
from
four
different
models:
Trites
etcetaceans
al.tonnes
(1997)from
(dotted
line);
Kenney
et
al.
(1997)
(solid
models:
Trites
et
al.
(1997)
(dotted
line);
Kenney
et
al.
(1997)
(solid
porpoise)
toInnes
100
tonnes
(e.g.
a blue
whale)
from
four
different
models:
Trites
et
al.
(1997)
(dotted
line);
Kenney
et
al.
(1997)
(solid
black
line);
et
al.
(1987)
(dashed
line);
and
Sigurjónsson
and
black
line);
Innes
et
al.
(1987)
(dashed
line);
and
Sigurjónsson
and
models:
Trites
et
al.
(1997)
(dotted
line);
Kenney
et
al.
(1997)
(solid
black
line);
Innes
et
al.
(1987)
(dashed
line);
and
Sigurjónsson
and
Víkingsson
(1997)
(alternating
long
and
short
dashes).
The
solid
grey
Víkingsson
(1997)
(alternating
long
and short
dashes).
The solid grey
black
line);
Innes
et
al.
(1987)
(dashed
line);
and
Sigurjónsson
and
Víkingsson
(1997)
and short
dashes).
Thean
solid
grey
line
represents
the(alternating
Kenney et
et long
al. (1997)
model
using
activity
line
represents
the
Kenney
al.
(1997)
model
using
an
activity
Víkingsson
(alternating
and short
dashes).
Thean
solid
grey
line
represents
the
Kenney
et long
al. (1997)
model
using
activity
multiplier
of(1997)
3.0instead
instead
of
2.5.
multiplier
of
3.0
of
2.5.
line represents
Kenney
et al. (1997) model using an activity
multiplier
of 3.0the
instead
of 2.5.
multiplier of 3.0 instead of 2.5.
Primary production required
Striped dolphin
The role of cetaceans within the food web of their ecosystem
An esw of 489m (CV=8.4%) was estimated for striped
was also examined by estimating the proportion of net primary
dolphins using a hazard-rate model without adjustment,
production required to sustain the prey that they consumed.
after truncation at 1,400m. Mean school size was 19.9
et al.: SEASONAL ESTIMATES OF 34
CETACEANS IN
IN THE
THE LIGURUIAN
LIGURIAN SEA
34
LARAN
OF
CETACEANS
34
LARAN et
et al.:
al.:
SEASONAL
ESTIMATES
OF
CETACEANS
IN
THE
LIGURUIAN
SEA
031-040 JNL LARAN 374:Layout
1 SEASONAL
29/12/09 ESTIMATES
14:11 Page
the
the Innes
Innes et
et al.
al. (1987)
(1987) model
model were
were also
also plausible.
plausible. Similarly,
Similarly, Table 1This
This was
was estimated
estimated using
using aa constant
constant transfer
transfer efficiency
efficiency of
of 10%
10%
031-040 JNL 374:Layout 1 29/12/09 14:11 Page 34
successive
trophic
levels,
TL
and
the
Kenney
has
used
for
the 374:Layout
Kenney
et al.
al.
(1997)
model
has been
been
used
for
the
between
successive
trophicFebruary
levels, 2001
TL (Pauly
(Pauly
and Christensen,
Christensen,
031-040 JNL
1 and(1997)
29/12/09
Page
34
Survey et
effort
on-effortmodel
total14:11
sightings
after truncation
(andthe
number ofbetween
individuals)
collected between
and February
2004.
-1)) to
principal
1995).
principal analyses
analyses reported
reported in
in this
this paper.
paper.
1995). The
The primary
primary production
production required
required (PPR
(PPRpp,, gC
gC m
m22 yy-1
to
Sperm* whale
Pilot whale Risso’s dolphin Striped dolphin
Total
Consumption
support
Consumption rates
rates were
were estimated
estimated using
using Eqns
Eqns (4)
(4) and
and (5),
(5),
support consumption
consumption of
of any
any prey
prey type
type pp was
was calculated
calculated from
from
April-September
3,967 fish;
77 (126)
19 (29)
6 (171)
4 (39)
(3,520)
and
partitioned
consumption
of
(Q
10
kk being
and
partitioned into
into three
three19prey
prey categories:
categories:
fish; cephalopod;
cephalopod;
consumption
of that
that prey
prey
(Qpp)) using
using a169
a factor
factor
10kk,, with
with275
being
October-March
12
2,235
8
(9)
8
(24)
0
6
(68)
74
(959)
96 =
and
zooplankton
(crustaceans).
In
the
absence
of
knowledge
the
number
of
trophic
steps
between
phytoplankton
(TL
and zooplankton (crustaceans).
In the absence
ofetknowledge
the
number ofOFtrophic
steps between
phytoplankton
(TL
= 1)
1)
34
LARAN
al.:
SEASONAL
ESTIMATES
CETACEANS
IN
THE
LIGURUIAN
SEA
31 rate, the6,202
(135)
27 (53)
6 (171)
10 (107)
243 (4,478)
371
on
variation
and
prey
onTotal
variation of
of the
the ingestion
ingestion
rate, the CVs
CVs were
were85propagated
propagated
and the
the given
given
prey category:
category:
*Both visual
sightings
and
acoustic
detections
aremodel
included
for sperm
whales.
the
Innes
et estimates
al.
(1987)
were
alsothe
plausible.
Similarly, IN THE
ThisLIGURUIAN
was estimated
using a constant transfer efficiency o
from
biomass
densities
through
to
from
biomass
densities
estimates
through
to
the
34
LARAN
et
al.:
SEASONAL
ESTIMATES
OF CETACEANS
SEA
34
LARAN
et
al.:
SEASONAL
ESTIMATES
OF used
CETACEANS
LIGURUIAN
SEA
the
Kenney
et
al.
(1997)
model
has
been
for the IN THE
between
successive
trophic levels, TL (Pauly and Christ
consumption
consumption estimates,
estimates, whilst
whilst aware
aware that
that the
the CV
CV value
value
the
Innes
et
al.
(1987)
model
were
also
plausible.
Similarly,
This
was
estimated
using
a
constant
transfer
efficiency
of 10%
principal
analyses
reported
in
this
paper.
1995).
The
primary
required
(PPR , gC m2
would
be
underestimated
by
an
unknown
and
maybe
would be underestimated
by
an SEASONAL
unknown and
maybe OF CETACEANS IN THE LIGURUIAN SEAproduction
34
LARAN
et al.:
ESTIMATES
(8) p
the Innes
etamount.
al.
model
were
also
plausible.
Similarly,
This
was(5),
estimatedsupport
using
aconsumption
constant
transfer
efficiency
of 10%
1http://www.fao.org/fishery/statistics/programme/3,1,2/en
the
Kenney
et (1987)
al. For
(1997)
has
beenestimated
used
for
the
successive
trophic
levels, TL
(Pauly
and
Christensen,
Consumption
were
using
(4) and
of any
prey
type
p(8)
was calculated
important
the
group
of
the
of
important
amount.
For
the model
grouprates
of species,
species,
the sum
sum
of Eqnsbetween
the Innes
Kenney
et al.
(1997)
has
been
used
for The
the
between
successive
trophic
levels,
TL
(Pauly
and
Christensen,
-1
1995).
The
primary
production
required
(PPR
gC
m22-2of
)
to 10k, with k
principal
reported
inmodel
thisinto
paper.
,,)gC
m
)
to
1995).
The
production
required
(PPR
and
partitioned
three
prey
categories:
consumption
of
prey
(Q
using
ayy-1
factor
the
et
model
were
also
plausible.
Similarly,
This
was
using
a constant
transfer
efficiency
10%
variances
of
the
different
components
were
estimated.
where
E
is
the
density
of
the
prey.
TL
the
trophic
variancesanalyses
ofal.
the(1987)
different
components
were
estimated.
The fish; cephalopod;
where
Eppestimated
isprimary
the energy
energy
density
ofthat
the
prey.
TL
is
the
trophic
pp
p is
-1) to
principal
analyses
reported
in
this
paper.
,
gC
m
y
1995).
The
primary
production
required
(PPR
p
Consumption
rates
were
estimated
using
Eqns
(4)
and
(5),
support
consumption
of
any
prey
type
p
was
calculated
from
and
zooplankton
(crustaceans).
In
the
absence
of
knowledge
the
number
of
trophic
steps
between
phytoplankton
(T
the
Kenney
et
al.
(1997)
model
has
been
used
for
the
between
successive
trophic
levels,
TL
(Pauly
and
Christensen,
estimated
level
estimated percentages
percentages of
of each
each species’
species’ diet
diet comprising
comprising the
level of
of the
the prey
prey category
category and
and assumed
assumed to
to be
be 2.2
2.2 for
for
Consumption
rates
wereprey
estimated
usingfish;
Eqns
(4)(Kenney
andCVs
(5), were1995).
support
consumption
of
any
prey
type
p(PPR
was
calculated
from
k,gC
2kybeing
-1
and
partitioned
into
three
categories:
cephalopod;
consumption
of
that
prey
(Q
)
using
a
factor
10
with
on
variation
of
the
ingestion
rate,
the
propagated
and
the
given
prey
category:
principal
analyses
reported
in
this
paper.
,
m
)
to
The
primary
production
required
three
categories
were
based
upon
previous
reviews
crustaceans,
3.2
for
cephalopods,
and
3.0
for
fish
(Pauly
and
three categories were based upon previous reviews (Kenney
crustaceans, 3.2 for cephalopods,
and 3.0 forpfish
(Pauly and
p
k, with
and
partitioned
into
three
prey
categories:
fish;
cephalopod;
consumption
oftrophic
that prey
(Q
) using
a factor
k being
pbetween
and
zooplankton
(crustaceans).
In thedensities
absence
knowledge
the
number
(TL
= 1)
from
estimates
to consumption
the of1995).
rates
were
estimated
using
Eqns
(4)
and (5),
support
ofsteps
any
prey
pdenominator
was10
calculated
from
et
al.,
1985;
et
al.,
1997;
Pauly
et
al.,
1998)
as
Christensen,
terms
in
the
denominator
converts
et Consumption
al.,
1985; Kenney
Kenney
et biomass
al.,
1997;
Pauly
et of
al.,
1998)
asthrough
Christensen,
1995). The
The
terms
intype
thephytoplankton
converts
and
zooplankton
(crustaceans).
In
the
absence
of
knowledge
the
number
of
trophic
steps
between
phytoplankton
(TL
=22 to
1)
k
on
variation
of
the
ingestion
rate,
the CVs
were
propagated
and
givenof
prey
category:
consumption
estimates,
whilst
aware that theconsumption
CVthe
value
and
partitioned
into
three
categories:
fish;
cephalopod;
that
preyunits
(Qp) (Platt,
using a1969)
factorand
10 ,from
with kkm
being
modified
by
and
data
specific
to
Mediterranean
from
energy
to
carbon
modified
by literature
literature
andprey
data
specific
to the
the
Mediterranean
from
energy
to
carbon
units
(Platt,
1969)
and
from
km
to
on
variation
of
the
ingestion
rate,
the
CVs
were
propagated
and
the
given
prey
category:
2
2
from
biomass
densities
estimates
through
to
the
would
be
underestimated
by
an
unknown
and
maybe
and
zooplankton
(crustaceans).
In
the
absence
of
knowledge
the
number
of
trophic
steps
between
phytoplankton
(TL
=
1)
Sea.
m
Sea. The
The food
food of
of fin
fin whales
whales in
in summer
summer was
was assumed
assumed to
to be
be
m .. The
The primary
primary production
production required
required was
was then
then compared
compared to
to
from
biomass
densities
estimates
through
the
consumption
whilst
aware
that
the
CVtoof
value
amount.
the
group
species, and
the
sum
of preyproduction
on
variation
ofestimates,
theimportant
ingestion
rate,
the For
CVs
were
propagated
category: as
100%
crustaceans,
as
euphausiid
Meganyctiphanes
total
net
primary
100%
crustaceans,
as the
the
euphausiid
Meganyctiphanes
totalthe
netgiven
primary
production
as reported
reported in
in the
the literature.
literature.
consumption
estimates,
whilst
aware
that
theand
CV
value
would
be is
by
an
unknown
variances
the
different
components
were estimated. The
where Ep is the energy density of the prey. TL is the t
from
biomass
densities
estimates
tomaybe
the
norvegica
considered
as
its
only
food
resource
(Astruc,
norvegica
isunderestimated
considered
as of
its
only
foodthrough
resource
(Astruc,
(8)
would
be
underestimated
by
an
unknown
and
maybe
important
For
the
group
of species,
of
estimated
percentages
of each
species’
diet comprising
the with
of the prey category and assumed
consumption
estimates,
whilst
aware
that
the
CVsum
value
2005;
Relini
and
Giordano,
1992).
Since
fin
whales
are
Comparison
fisheries
(8) to be 2
2005; Orsi
Orsiamount.
Relini
and
Giordano,
1992).
Since
finthe
whales
are
Comparison
withlevel
fisheries
important
amount.
For
the
group
of
species,
the
sum
of
variances
theMediterranean
different
components
were
The
where
Eglobal
is thecapture
energy
density
of the
prey. TLwere
is the
trophic
three categories
based
upon
(Kenney
crustaceans,
3.2
for
cephalopods,
and
3.0 for fish (Pau
would
underestimated
by Sea
anwere
unknown
andprevious
maybe
present
in
in
winter
and
there
is
Annual
production
estimates
extracted
present be
inofthe
the
Mediterranean
Sea
in
winterestimated.
and
there
is reviews
Annual
capture
production
estimates
were
extracted
pglobal
(8)
variancesof
of
the different
components
were
estimated.
The
where
Ep as
is theprey
energy
densityand
of the
prey.
TLthe
is in
the
trophic
11category
estimated
percentages
each
diet
comprising
the
level
of
the
assumed
2.2
for
al.,ofthe
1985;
Kenney
et to
al.,
1997;
Pauly
1998)
Christensen,
1995).
The of
terms
the
denominator
co
important
amount.
For
group
ofclose
species,
the (Canese
sum
of et al.,
with
FishStat
Plus
and
series
Food
and
evidence
winter
at
least
Sicily
evidence of
winteretfeeding,
feeding,
at species’
least
close
to
Sicily
(Canese
with
FishStat
Plus
and the
the time
time
series
of to
thebe
Food
and
estimated
percentages
of
each
species’
diet
comprising
the
level
of
the
prey
category
and
assumed
to
be
2.2
for and from k
three
were
basedcomponents
upon
previous
reviews
(Kenney
crustaceans,
3.2
for
cephalopods,
3.0 for
fish
(Pauly
and
modified
by
literature
and
data
specific
to the Mediterranean
from
energy
to
carbon
units
1969)
variances
of theno
different
estimated.
The
where
Ep is the
energy
density
of and
the
prey.
TL
is(Platt,
the
trophic
Agriculture
Organisation
of
United
Nations
(FAO),
et
2006),
scaling
factor
was
applied
to
increase
et al.,
al.,categories
2006),
no
scaling
factor
was were
applied
to
increase
Agriculture
Organisation
of the
the
United
Nations
(FAO),
three
were
based
upon
reviews
(Kenney
crustaceans,
3.2
for 2cephalopods,
and
3.0
for fish
(Pauly
and
et
al.,categories
1985;
Kenney
et
al.,
1997;
Pauly
etcomprising
al.,
1998)
as
Christensen,
1995).
The
terms
in
the
denominator
converts
Sea.to
food
ofprevious
fin
whales
in summer
was assumed
to be
. The
primary
production
was
estimated
percentages
of
each
species’
dietfasting.
level
of
the
prey
category
and
assumed
torequired
be
2.2
for
available
from
the
Results
were
averaged
from
2000
to
summer
feeding
rate
account
for
winter
Based
on
available
from
themarea.
area.
Results
were
averaged
from
2000
tothen compa
summer
feeding
rate
toThe
account
for
winter
fasting.
Basedthe
on
et
al.,
1985;
Kenney
et
al.,
1997;
Pauly
et
al.,
1998)
as
Christensen,
1995).
The
terms
in
the
denominator
converts
2
modified
by
literature
and
data
specific
to
the
Mediterranean
from
energy
to
carbon
units
(Platt,
1969)
and
from
km
to
100%
crustaceans,
as
the
euphausiid
Meganyctiphanes
total
net
primary
production
as
reported
in the literatu
three
categories
were
based
upon
previous
reviews
(Kenney
crustaceans,
3.2
for
cephalopods,
and
3.0
for
fish
(Pauly
and
2005
information
2005 for
for two
two different
different areas:
areas: (1)
(1) the
the total
total Mediterranean
Mediterranean 2Sea
Sea
information for
for other
other areas
areas (Lockyer,
(Lockyer, 2007;
2007; Sigurjónsson
Sigurjónsson
modified
by literature
and
data
specific
towas
the
Mediterranean
from
energy
to global
carbon
units
(Platt,
1969)
and compared
fromconverts
km
to
2. (Astruc,
Sea.
The
food
of
fin
whales
in
summer
assumed
to
be
m
The
primary
production
required
was
then
to
norvegica
is
considered
as
its
only
food
resource
et
al.,
1985;
Kenney
et
al.,
1997;
Pauly
et
al.,
1998)
as
1995).
The
terms
in
the
denominator
Christensen,
terms
in
the
denominator
convert
plus
Black
Sea
dataset
of
Capture
Production
(1950and
Víkingsson,
1997;
Viale,
1985),
it
was
assumed
that
plus
Black Sea global dataset of Capture Production (1950and Víkingsson, 1997; Viale, 1985), it was assumed that
2. The
Sea. The
food
of fin
whales
in
summer
was
assumed
to Since
be finfrom
mwhales
primary
production
required
wasinthen
compared
to
100%
crustaceans,
as
the
euphausiid
Meganyctiphanes
total
net
primary
production
as
reported
the literature.
Orsi
Relini
andon
Giordano,
1992).
are
Comparison
with
fisheries
modified
by
literature
and
data
specific
to
the
Mediterranean
energy
to carbon
units
(Platt,
1969)
and
from
km2 to
2006);
(2)
total
fishery
production
(1950-2006)
considering
during
fin
whales
feed
mainly
euphausiids
(90%)
2006);
(2)
total
fishery
production
(1950-2006)
considering
during winter,
winter,
fin 2005;
whales
feed
mainly
on
euphausiids
(90%)
100%
crustaceans,
as
the
euphausiid
Meganyctiphanes
total
net
primary
production
as
reported
in
the
literature.
2
norvegica
is considered
as
foodwas
resource
(Astruc,
present
in its
theonly
Mediterranean
Sea
in
and
is industrial,
Annual
global
capture
estimates
m
. there
The primary
production
required
wasproduction
then
to were ext
Sea.
The food
of on
fin fish
whales
in
summer
assumed
to winter
be
commercial,
recreational
captures
and
aquaculture
but
when
available
(10%).
For
sperm
commercial,
industrial,
recreational
captures
andcompared
aquaculture
but occasionally
occasionally
on
fish
when
available
(10%).
For
sperm
norvegica
is
considered
as
only
food
resource
(Astruc,
1 and
2005;
Orsi
Relini
andbeen
1992).
Since
fin
whales
are to Sicily
Comparison
with
fisheries
with
Plus
evidence
ofitseuphausiid
winter
at least
close
theliterature.
time
series
total
net primary
production
as reported
in
the
100%
crustaceans,
asGiordano,
the
Meganyctiphanes
and
other
kinds
of
fish
farming
(FAO,
2008);
and
the
whales,
there
have
reports
on
two
stomach
contents
and(Canese
other
kinds
of
fishFishStat
farming
(FAO,
2008);
and (3)
(3)
the of the Foo
whales,
there
have
been
reports
on feeding,
two
stomach
contents
2005;the
Orsi isRelini
andal.,
Giordano,
1992).
Since
fin
whales
are
Comparison
with
fisheries
present
theconsidered
Mediterranean
Sea
winter
and
there
is
Annual
global
production
estimates
were
et
2006),
no in
scaling
factor
was
applied
to increase
Agriculture
Organisation
theextracted
United
norvegica
as
its
only
food
resource
(Astruc,
Sardinia
region
alone
(Tyrrhenian
Sea
to
Sardinia
and
from
Sea
(Astruc,
2005;
Roberts,
2003);
Sardinia
regioncapture
alone
(Tyrrhenian
Sea
to east
east of
of
Sardinia
and Nations (
from theinMediterranean
Mediterranean
Sea
(Astruc,
2005;
Roberts,
2003);
present
in
the
Mediterranean
Sea
in
winter
and
there
is
Annual
global
capture
production
estimates
were
extracted
1
evidence
ofRelini
winter
feeding,
at least
close
to Sicily
with
FishStat
and
the
time
series
of
the
Food
and
summer
feeding
rate
toSince
account
for(Canese
winter
Based
on
available
from
the
area.
Results
were
averaged
from 2
Comparison
fisheries
2005;
and
Giordano,
1992).
fin
whales
are fasting.
Corsica;
Fig.
1)
extracted
from
GFCM
(Mediterranean
both
included
only
cephalopods,
mainly
Histioteuthis
Corsica;
Fig. with
1)Plus
extracted
from
GFCM
(Mediterranean
and
both Orsi
included
only
cephalopods,
mainly
Histioteuthis
1 and the time series of the Food and
evidence
winter
feeding,
atfor
least
close
toconsumption
Sicily
(Canese
with FishStat
Plus
et
al., 2006),
no
scaling
factor
applied
to increase
Agriculture
Organisation
of the
United
Nations
(FAO),
information
other
areas
(Lockyer,
2007;
Sigurjónsson
2005
for two
different
areas:
(1) the
total Mediterrane
Annual
global
capture
production
estimates
were
extracted
present
inof
the
Mediterranean
Sea
in
winter
and
there
is
Black
Capture
Production
(1970-2005)
(FAO,
2008).
bonnellii.
However,
to
for
possible
of
Black Sea)
Sea)
Capture
Production
(1970-2005)
(FAO,
2008).
bonnellii.
However,
to account
account
forwas
possible
consumption
of
et al.,as 2006),
norate
scaling
factor
applied
to
increase
Agriculture
Organisation
ofSea
the
United
(FAO),
1 and
available
from
the
area.
Results
were
averaged
from
2000
toProduction
summer
to
account
forwas
winter
fasting.
Based
onwas assumed
and
1997;
Viale,
1985),
ital.,
that
plus
Black
global
dataset
ofto
Capture
with
Plus
the
time
series
ofNations
the
Food
and
evidence
winter
feeding,
at least
close
to
Sicily
(Canese
Total
fisheries
production
values
were
converted
rates
by
fish,
is
in
the
Ocean
(Clarke
et
Total FishStat
fisheries
production
values
were
converted
to
rates
by
fish, as feeding
isofreported
reported
inVíkingsson,
the Atlantic
Atlantic
Ocean
(Clarke
et al.,
available
from
the
area.
Results
were
averaged
from
2000
to
summer
feeding
rate
to
account
for
winter
fasting.
Based
on
2005
for
two
different
areas:
(1)
the
total
Mediterranean
Sea
information
for
other
areas
(Lockyer,
2007;
Sigurjónsson
during
winter,
fin
whales
feed
mainly
on
euphausiids
(90%)
2006);
(2)
total
fishery
production
(1950-2006)
consi
Agriculture
Organisation
of
the
United
Nations
(FAO),
et
al.,
2006),
no
scaling
factor
was
applied
to
increase
dividing
by
the
respective
surface
area.
Surface
area
for
the
1993),
it
was
assumed
that
90%
of
the
diet
is
cephalopods
dividing by the respective surface area. Surface area for the
1993), it was assumed that 90% of the diet is cephalopods
2005
for
two
different
areas:
(1)
the
total
Mediterranean
Sea
information
for
other
areas
(Lockyer,
2007;
Sigurjónsson
2
2 (Aubouin
plus
Seathe
global
dataset
Capture
Production
(19501997;
Viale,whales
1985),
it was
assumed
that
but
fish
when
available
For Black
sperm
commercial,
industrial,
recreational
captures
from
area.
Results
were
averaged
from 2000
to and aquac
summer
rate
tooccasionally
account
for on
winter
fasting.
Based
on(10%).available
and
Mediterranean
and
Black
Sea
2,966,000km
and
10%
is
For
pilot
and
Risso’s
dolphins,
(Aubouin
and
Mediterranean
and
Black
Sea is
isof
2,966,000km
and Víkingsson,
10%feeding
is fish.
fish.
For
pilot
whales
and
Risso’s
dolphins,
pluscontents
Black
Sea
global
dataset
ofarea
Capture
Production
(1950and Víkingsson,
1997;
Viale,
1985),
it2007;
was
assumed
thatstomach
2006);
total
fishery
production
(1950-2006)
considering
during
winter,
whales
feed
mainly
on
euphausiids
(90%)
and other
kinds
of
fishthe
farming
(FAO,
whales,
there
have
been
reports
two
2005
for(2)two
different
areas:
(1)
the
total
Mediterranean
Sea2008); and (
information
forfinother
areas
(Lockyer,
Sigurjónsson
Durand-Delga,
2002).
Surface
for
Sardinia
region
based
aa small
sample
in
the
Mediterranean
Sea
(Astruc,
Durand-Delga,
2002).
Surface
area
for
the
Sardinia
region
based on
on
small
sample
in
the
Mediterranean
Sea on
(Astruc,
2006);
(2)
total
fishery
production
(1950-2006)
considering
during
winter,
fin
whales
feed
mainly
on
euphausiids
(90%)
2
2
commercial,
industrial,
recreational
captures
and
aquaculture
but
occasionally
on
fish
when
available
(10%).
For
sperm
Sardinia
region
alone
(Tyrrhenian
Sea
to east of Sardin
from
the
Mediterranean
Sea
(Astruc,
2005;
Roberts,
2003);
plus
Black
Sea
global
dataset
of
Capture
Production
(1950and
Víkingsson,
1997;
Viale,
1985),
it
was
assumed
that
was
2005;
was estimated
estimated with
with ArcView
ArcView 9.2
9.2 as
as 288,750km
288,750km ..
2005; Orsi
Orsi Relini
Relini and
and Garibaldi,
Garibaldi, 1992)
1992) and
and the
the earlier
earlier
commercial,
industrial,
captures
and
aquaculture
but occasionally
on
fishincluded
when
available
(10%).
For
sperm
and
other
of
fishrecreational
farming
2008);
and
(3) the
whales,
there
been
reports
on
two
stomach
contents
only
cephalopods,
mainly Histioteuthis
Corsica;
Fig. 1)(FAO,
extracted
fromconsidering
GFCM
(Mediterranea
2006);
(2) kinds
total
fishery
production
(1950-2006)
during
winter,
fin
whales
feed
mainly
onand
euphausiids
(90%)
reviews,
diets
of
95%
cephalopods
5%
were
reviews,
dietshave
ofboth
95%
cephalopods
and
5% fish
fish
were
and
other
kinds
of
fish
farming
(FAO,
2008);
and
(3) and
the
whales,
there
have
been
reports
on
two
stomach
contents
Sardinia region
alone
(Tyrrhenian
Sea
toProduction
eastand
of Sardinia
from
the Mediterranean
Sea
(Astruc,
2005;
Roberts,
2003);
Black
Sea) Capture
(1970-2005)
(FAO,
bonnellii.
However,
to
for possible
of industrial,
commercial,
recreational
captures
aquaculture
but
occasionally
on
when
available
(10%).
For
sperm
assumed.
The
of
striped
dolphins
in
the
Ligurian
Sea
assumed.
The food
food
offish
striped
dolphins
in account
the
Ligurian
Sea is
is consumption
RESULTS
Sardinia
region
(Tyrrhenian
Sea to (Mediterranean
east
of Sardinia
and
from the
Mediterranean
Sea
2005;
Roberts,
2003);
RESULTS
Corsica;
Fig.
1)alone
extracted
from GFCM
both
included
only
cephalopods,
mainly
Histioteuthis
Total
fisheries
production
values
converted
to ra
fish,
as
is (Astruc,
reported
in the
Atlantic
et al.,
and
other
kinds
of
fish
farming
(FAO,
2008);
andwere
(3) and
the
whales,
there
been
reports
on cephalopods
two
stomach
contents
comprised
of
49.3%
fish,
49.7%
and
1%
comprised
of have
49.3%
fish,
49.7%
cephalopods
andOcean
1% (Clarke
Corsica;
Fig.Capture
1)alone
extracted
from
and
both the
included
only
cephalopods,
mainly
Histioteuthis
Black
Sea)
Production
(1970-2005)
2008).
bonnellii.
However,
to account
for
possible
consumption
dividing
by
theGFCM
respective
area.
Surface area
1993),
it was
assumed
thatRoberts,
90%
of2003);
the of
diet is cephalopods
Sardinia
region
(Tyrrhenian
Sea
to (Mediterranean
east surface
of(FAO,
Sardinia
and
from
Mediterranean
Sea
(Astruc,
2005;
Density,
biomass
and
prey
consumption
crustaceans
(Würtz
and
Marrale,
1993).
Density,
biomass
and
prey
consumption
crustaceans
(Würtz
and
Marrale,
1993).
Black
Sea)
Production
(1970-2005)
2008).
bonnellii.
to
account
for possible
consumption
ofRisso’s
Total
fisheries
values
were
converted
to
rates
by
fish,
isHowever,
reported
in10%
the Atlantic
Ocean
(Clarke
al.,
Mediterranean
and
Black
Sea(FAO,
is
2,966,000km
and
is fish.
For
pilot
whales
dolphins,
Corsica;
Fig.Capture
1)production
extracted
from GFCM
(Mediterranean
and
both
included
cephalopods,
mainly
Histioteuthis
During
these
surveys,
371
(or
acoustic
detections
in
The
daily
prey
consumption
rate
each
species
in
each
During
these
surveys,
371 sightings
sightings
(or
acoustic
detections
in 2 (Aubou
Theas
daily
preyonly
consumption
rate for
for
each
species
inetand
each
Total
fisheries
production
values
were
converted
to
rates
by
fish,
as
is
reported
in
the
Atlantic
Ocean
(Clarke
et
al.,
-2
-1
-2 for
dividing
by
the
respective
surface
area.
Surface
area
for
the
1993),
it was
assumed
that
of))possible
the
isthe
cephalopods
Durand-Delga,
2002).
Surface
area
for
the Sardinia
based
onkm
a90%
small
sample
inconsumption
Mediterranean
Sea
Black
Sea)
Production
(FAO,
2008).
bonnellii.
However,
to kg
account
of
dd-1
was
then
estimated
by
the
case
of
sperm
whales)
were
recorded
(Table
1).
Five
six-month
season
(in
wasdiet
then
estimated
the (Astruc,
case
of Capture
sperm
whales)
were(1970-2005)
recorded
(Table
1).
Five
six-month
season
(in
kg
km
dividing
by
theproduction
respective
surface
area.
Surface
forand
the
1993),
assumed
that
90%
of the
is cephalopods
2 (Aubouin
2.
Mediterranean
and
Black
Sea
is 2,966,000km
and
10%
isreported
fish.
For
pilot
whales
and
Risso’s
dolphins,
was
estimated
with
ArcView
9.2area
288,750km
2005;
OrsiAtlantic
Relini
anddiet
Garibaldi,
the earlier
fisheries
values
were
converted
toasdolphins
rates
by
fish,
asitiswas
in density
the
Ocean
(Clarke
et1992)
al., and Total
multiplying
seasonal
by
ration.
Seasonal
cetacean
species
were
recorded
on-effort.
Striped
multiplying
seasonal
density
by daily
daily
ration.
Seasonal
cetacean
species
were
recorded
on-effort.
Striped
dolphins
2 (Aubouin
Mediterranean
and
Black
Sea
is
2,966,000km
and
and
10%
is
fish.
For
pilot
whales
and
Risso’s
dolphins,
Durand-Delga,
2002).
Surface
area
for
the
Sardinia
region
based
on
a
small
sample
in
the
Mediterranean
Sea
(Astruc,
reviews,
diets
of
95%
cephalopods
and
5%
fish
were
dividing
by
the
respective
surface
area.
Surface
area
for
the
1993),
it
was
assumed
that
90%
of
the
diet
is
cephalopods
consumption
were
consumption was
was calculated
calculated by
by multiplying
multiplying daily
daily rates
rates by
by
were the
the most
most frequently
frequently observed
observed (n=243
(n=243 sightings),
sightings), followed
followed
Durand-Delga,
2002).
Surface
forRisso’s
the Sardinia
region
based
on
aissmall
sample
inThe
the
Mediterranean
Sea
(Astruc,
2dolphins
2 (Aubouin
was
estimated
with
ArcView
9.2
as(27),
288,750km
.
2005;
Orsi
Relini
and
Garibaldi,
1992)
anddolphins
the
earlier
assumed.
food
of
in
Sea
is (85),
Mediterranean
and
Black
Sea
is area
2,966,000km
and
and
10%
fish.
For
whales
andstriped
Risso’s
dolphins,
the
of
days
in
each
six-month
period
(182.5),
and
by
whales
sperm
whales
(10)
the number
number
of
days
in pilot
each
six-month
period
(182.5),
andthe Ligurian
by fin
fin
whales
(85),
sperm
whales
(27),
Risso’s
dolphins
(10)
2
RESULTS
was
estimated
with
ArcView
9.2
as
288,750km
.
2005;
Orsi
Relini
and
Garibaldi,
1992)
and
the
earlier
-2
-1
-2were
reviews,
95% rate
cephalopods
5%
comprised
of Mediterranean
49.3%and
fish,in
cephalopods
1% pilot
Durand-Delga,
2002).
Surface
Sardinia
region
based
on adiets
smallofsample
in
the
Sea
(Astruc,
the
consumption
per
species
(Q,
kg
km
yy-1))
and
finally
whales
(6),
the
only
that
was
the annual
annual
consumption
rate
per
species
(Q,
in 49.7%
kgfish
km
andand
finally
pilot
whales
(6), area
the for
onlythespecies
species
that
was
reviews,
diets
ofcrustaceans
95%
cephalopods
5% the
fish
were
2was
assumed.
The
food
striped
dolphins
inand
the
Ligurian
Sea
is
Density,
biomass
and prey
consumption
(Würtz
and
Marrale,
1993).
was
estimated
with
ArcView
9.2
assurvey
288,750km
. 2,235km
2005;
Orsi
Relini
Garibaldi,
1992)
and
earlier
was
the
sum
of
the
winter
and
values,
with
the
encountered
in
summer
only.
Total
effort
was then
then
the
sum
ofofand
the
winter
and summer
summer
values,
with
the
encountered
in
summer
only.
Total
survey
effort
was
2,235km
RESULTS
assumed.calculated
The
striped
dolphins
inand
the 5%
Ligurian
Sea
is species
comprised
of food
49.3%
fish,
49.7%
cephalopods
and
1%
During
surveys,
371April-September.
sightings (or acoustic detect
The
daily
prey
consumption
rate
for
each
in October-March
each
reviews,
diets
of of
95%
cephalopods
fish
were
variance
as
the
sum
of
seasonal
variances.
during
and
3,967km
during
RESULTS
variance calculated
as
the
sum
of the
the
seasonal
variances.
during
October-March
andthese
3,967km
during
April-September.
comprised
of
49.3%
fish,
49.7%
cephalopods
and
1%
-2 d-1) Sea
Density, biomass
andcase
preyofconsumption
crustaceans
(Würtz
and
Marrale,
1993).
wasisthen estimated
by
the
sperm whales) were recorded (Table 1)
season
(ininkg
assumed.
The
foodsix-month
of
striped
dolphins
thekm
Ligurian
RESULTS
Density,
biomass
and371
prey
consumption
crustaceans
(Würtz
and
Marrale,
1993).
During
these
surveys,
sightings
(or acoustic
detections
in Striped do
The daily
prey
consumption
rate
for
each
species
indaily
each
multiplying
seasonal
density
byand
Seasonal
cetacean
species
were
recorded
on-effort.
comprised
of
49.3%
fish,
49.7%
cephalopods
1% ration.
Primary
production
required
Striped
dolphin
Primary
production
required
Striped
dolphin
During
these
surveys,
371
sightings
(orestimated
acoustic
detections
in
The
daily
prey
consumption
rate
for
each
species
in
each
-2
-1
d
)
was
then
estimated
by
the
case
sperm
whales)
were
recorded
(Table
1).
Five
six-month
(in
kgMarrale,
kmthe
consumption
was
calculated
by
multiplying
daily
rates
by
were
the
most
frequently
observed
(n=243
sightings), fo
Density,
biomass
and
prey
consumption
crustaceans
(Würtz
and
1993).
The
cetaceans
within
food
web
of
their
ecosystem
An
esw
of
489m
(CV=8.4%)
was
for
striped
The role
role of
ofseason
cetaceans
within
the
food
web
of
their
ecosystem
An
esw
of
489m
(CV=8.4%)
was
estimated
for
striped
-2 d-1) was then estimated by
the
case
of
sperm
whales)
were
recorded
(Table
1).
Five
six-month
season
(in
kg
km
multiplying
seasonal
density
by
daily
ration.
Seasonal
cetacean
species
were
recorded
on-effort.
Striped
dolphins
the
number
of
days
in
each
six-month
period
(182.5),
and
by
fin
whales
(85),
sperm
whales
(27),
Risso’s
dolphin
During
these
surveys,
371
sightings
(or
acoustic
detections
in
The
daily
prey
consumption
rate
for
each
species
in
each
was
dolphins
was also
also examined
examined by
by estimating
estimating the
the proportion
proportion of
of net
net primary
primary
dolphins using
using aa hazard-rate
hazard-rate model
model without
without adjustment,
adjustment,
multiplyingseason
seasonal
density
by
daily
ration.
Seasonal
cetacean
species
were
recorded
on-effort.
Striped
dolphins
-2
-1
-2
-1
consumption
was
calculated
by
multiplying
daily
rates
were
the
most
frequently
observed
(n=243
sightings),
followed
the
annual
consumption
rate
per
species
(Q,
in
kg
km
y
)
and
finally
pilot
whales
(6),
the
only
species
tha
d
)
was
then
estimated
by
the
case
of
sperm
whales)
were
recorded
(Table
1).
Five
six-month
(in
kg
km
production
required
to
sustain
the
prey
that
they
consumed.
after
truncation
at
1,400m.
Mean
school
size
was
19.9
production required
consumed.
after truncation at 1,400m. Mean school size was 19.9
consumption
was
calculated
by
multiplying
daily
rates
by values,
were
the
most
frequently
observed
(n=243
sightings),
followed
the
number of
days
inthen
eachthesix-month
(182.5),
and
by
fin
whales
(85),were
sperm
whales
(27), Risso’s
dolphins
(10)effort was 2,2
was
sum
of
theperiod
winter
and
summer
with
the
encountered
in summer
only.
Total
survey
multiplying
seasonal
density
by
daily
ration.
Seasonal
cetacean
species
recorded
on-effort.
Striped
dolphins
the annual
numberconsumption
ofwas
days
in each
six-month
(182.5),
by finfinally
(85),during
sperm
whales
(27),
Risso’s
dolphins
(10)
-1)
the
rate
per
(Q,sum
indaily
kg
yand
and
whales
(6), the
only
species
that
wasApril-Septem
variance
calculated
as period
the
ofkm
the-2
seasonal
variances.
October-March
and
3,967km
during
consumption
calculated
by species
multiplying
rates
by
were
thewhales
mostpilot
frequently
observed
(n=243
sightings),
followed
-2 y-1)
the number
annual
rate six-month
perand
species
(Q,values,
in (182.5),
kg km
andfinfinally
pilot
whales
(6),
the
only
species
that
was
was
then theconsumption
sum
of the
winter
summer
withand
the Table
encountered
in
summer
only.
Total
survey
effort
was
2,235km
the
of
days
in each
period
by
whales
(85),
sperm
whales
(27),
Risso’s
dolphins
(10)
Table 11
was
then
the
sum
of
the
winter
and
summer
values,
with
the
encountered
in
summer
only.
Total
survey
effort
was
2,235km
-2 y-1)
variance
calculated
ason-effort
therate
sum
ofspecies
the seasonal
variances.
during
October-March
andFebruary
3,967km
during
April-September.
production
required
dolphin
the
annual
consumption
per
(Q,
kg km(and
finally
pilot Striped
whales
(6), the
only
species2004.
that was
Survey
effort
and
total
after
truncation
number
individuals)
collected
between
2001
and
Survey
effortPrimary
and
on-effort
total
sightings
after in
truncation
(and
number of
ofand
individuals)
collected
between
February
2001
and February
February
2004.
variance
the
sum
ofsightings
the
seasonal
variances.
during
October-March
and
3,967km
during
April-September.
role
of cetaceans
within
the
food
ecosystem
An esw
ofTotal
489m
(CV=8.4%)
estimated for s
in summer
only.
survey
effort
waswas
2,235km
was
then calculated
the sum The
of as
the
winter
and
summer
values,
withweb
theof theirencountered
Seasonal
No.
of
Effort
(km)
Fin
whale
Sperm*
Pilot
whale
Risso’s
dolphin
Total
Seasonal period
period
No.required
of surveys
surveys
Effort
(km)
Finthe
whale
Sperm*
whale
Pilot
whale dolphins
Risso’s
dolphin
Striped
dolphin
Total without adjus
Primary
production
Striped
dolphin
was
also
examined
byseasonal
estimating
proportion
ofwhale
net primary
using Striped
aduring
hazard-rate
model
during
October-March
anddolphin
3,967km
April-September.
variance
calculated
as
the
sum
of the
variances.
Primary
required
Striped
The
role ofproduction
cetaceans
within
food3,967
web
of their
ecosystem
An
esw dolphin
489mafter
(CV=8.4%)
was
for275
striped
production
required
to sustain
the
prey that 19
they
consumed.
at
1,400m.
Mean
school size was
April-September
19
77
(126)
(29)
66of
(171)
44truncation
(39)
169
(3,520)
April-September
19 the
3,967
77
(126)
19
(29)
(171)
(39)
169estimated
(3,520)
275
The
role
of
cetaceans
within
the
food
web
of
their
ecosystem
An
esw dolphin
of
(CV=8.4%)
was74
estimated
for 96
striped
October-March
12
2,235
88 (9)
00 489m
66 (68)
October-March
12
2,235
(9)
(24)
(68)
74 (959)
(959)
96
was
also examined
by estimating
the proportion
of net
primary 88 (24)
dolphins
using
a hazard-rate
model
without
adjustment,
Primary
production
required
Striped
was
also examined
bytowithin
estimating
theprey
proportion
of85
net
primary 27
dolphins
using
aat hazard-rate
model
without
Total
31
6,202
(135)
66of
(171)
10
243
(4,478)
371
Total
31 thethe
6,202
85
(135)
27 (53)
(53)
(171)
10 (107)
(107) Mean
243
(4,478)
371
production
sustain
that
consumed.
after
truncation
1,400m.
school
sizeadjustment,
was
19.9
The
role
of required
cetaceans
food
web
of they
their
ecosystem
An
esw
489m
(CV=8.4%)
was
estimated
for
striped
production
required
to
sustain
the
prey
that
they
consumed.
after
truncation
at
1,400m.
Mean
school
size
was
19.9
*Both
visual
sightings
and
acoustic
detections
are
included
for
sperm
whales.
*Both
visual
sightings
and
acoustic detections
are included
for sperm
whales. dolphins using
was
also
examined
by
estimating
the
proportion
of
net
primary
a
hazard-rate
model
without
adjustment,
Table
1
MATES OF CETACEANS IN THE LIGURUIAN SEA
production required to sustain
the
prey
that
they
consumed.
after
truncation
at
1,400m.
Mean
school
size
was
19.9
Survey effort and on-effort total sightings after truncation (and number of individuals) collected between February 2001 and February 2004.
ilarly,
This was estimated using a constant transfer efficiency of 10% Table 1
Seasonal period
No. of surveys Effort (km)Table Fin
whale
Sperm* whale
Pilot whale Risso’s dolphin Striped dolphin
To
11http://www.fao.org/fishery/statistics/programme/3,1,2/en
http://www.fao.org/fishery/statistics/programme/3,1,2/en
or the
betweenSurvey
successive
trophic
levels,
TL (Pauly
Christensen,
effort and
on-effort
total sightings
afterand
truncation
(and number of 1individuals)
collected between February 2001 and February 2004.
Survey
effort
and
on-effort
total
sightings
after
truncation
(and
number
of
individuals)
collected
between
February
2001
and
February
2004.
2
-1
19 p, gC m y3,967
19 (29)
6 (171)
4 (39)
169 (3,520)
27
) to Table 177 (126)
1995). The primary April-September
production required (PPR
Seasonal period
No. of surveys Effort (km)
Fin whale2,235Sperm* whale
whale
Risso’s dolphin
Striped dolphin
Total74 (959)
October-March
12 calculated
8 (9) Pilot
8 (24)between
0
6February
(68)
9
nd (5),
support
consumption
of
prey
type
p (km)
was
from
Survey
effort and
on-effort
total sightings
after
truncation
(and
number
individuals)
February
2001
anddolphin
2004.
Seasonal
period
No.
ofany
surveys
Effort
Fin whale
Sperm*ofwhale
Pilotcollected
whale
Risso’s dolphin
Striped
Total
85 (135) 6 (171)
27 (53)
10 (107)
243 (4,478)
37
April-September
(126)
4 (39)6 (171) 169 (3,520)
275
opod;
consumption
of thatTotal
prey 19
(Qp) using a3,967
factor3110k, 77
with
k 6,202
being 19 (29)
031-040 JNLSeasonal
374:Layout
29/12/09
Page 34
period 1 No.
of surveys 14:11
Effort (km)
Fin whale
April-September
Seasonal
period
October-March
19
3,967
77
(126)
19
(29)
6whales.
(171)
No. of12
surveys
Effort
(km)
whale
Pilot
*Both
visual
sightings
and
acousticFin
detections
areSperm*
included
for sperm
2,235
8whale
(9)
8 (24)
0whale
(39)
Risso’s
dolphin
64 (68)
169
Striped
dolphin
74 (3,520)
(959)
275
Total
96
J. CETACEAN RES. MANAGE.
11(1):31–40,
2009
MANAGE. 11(1):31–­­
11(1):31–40,
2009
J. CETACEAN
CETACEAN RES. MANAGE.
40, 2010
35
35
Table
Table 2
2
Mean body
body masses
masses (W,
(W, in
in kg)
kg) for
for males,
males, females,
females, and
and both
both sexes
sexes averaged,
averaged, for
for five
five cetacean
cetacean species
species in
in the
the Ligurian
Ligurian Sea,
Sea, and
and
Mean
-1
mean
-1,, and
mean daily
daily ration
ration per
per individual
individual (kg
(kg d
d-1
and as
as %
% of
of body
body mass
mass in
in parentheses)
parentheses) estimated
estimated from
from four
four different
different models:
models: (1)
(1) Innes
Innes
et
et al.
al. (1987);
(1987); (2)
(2) Trites
Trites et
et al.
al. (1997);
(1997); (3)
(3) Kenney
Kenney et
et al.
al. (1997);
(1997); (4)
(4) Sigurjónsson
Sigurjónsson and
and Víkingsson
Víkingsson (1997).
(1997). Model
Model 3
3 (in
(in bold)
bold) was
was
selected for
for use
use in
in the
the analysis
analysis reported
reported in
in this
this paper.
paper. Mean
Mean body
body masses
masses were
were taken
taken from
from Trites
Trites and
and Pauly
Pauly (1998)
(1998) or
or estimated
estimated
selected
using
, in cm) from Mediterranean specimens (F. Dhermain, GECEM and
using their
their regression
regression models
models from
from maximum
maximum lengths
lengths (L
(Lmax
max
max, in cm) from Mediterranean specimens (F. Dhermain, GECEM and
O.
comm.).
O. Van
Van Canneyt,
Canneyt, CRMM,
CRMM,-pers.
pers.
comm.).
University
of La Rochelle, pers. comm.).
Lmax
W
Daily ration
max
Lmax
W
Daily ration
Species
�
�
�
�
Mean
(1)
(2)
(3)
(4)
Species
�
�
�
�
Mean
(1)
(2)
(3)
(4)
Fin whale
2,000
2,000
31,429
30,832
31,131
484 (1.6)
393 (1.3)
410 (1.3)
680 (2.2)
Fin whale
2,000
2,000
31,429
30,832
31,131
484 (1.6)
393 (1.3)
410 (1.3)
680 (2.2)
Sperm whale
1,500
na
16,083
10,098
12,492
233 (1.9)
189 (1.5)
244 (2.0)
393 (3.1)
Sperm whale
1,500
na
16,083
10,098
12,492
233 (1.9)
189 (1.5)
244 (2.0)
393 (3.1)
Pilot whale
whale
600
500
689
450
546
19.0 (3.5)
(3.5) 15.5
15.5 (2.8)
(2.8) 23.6
23.6 (4.3)
(4.3) 34.2
34.2 (6.3)
(6.3)
Pilot
600
500
689
450
546
19.0
Risso’s dolphin
na
na
236
211
224
9.3 (4.2)
7.6 (3.4)
12.1 (5.4) 17.0 (7.6)
Risso’s dolphin
na
na
236
211
224
9.3 (4.2)
7.6 (3.4)
12.1 (5.4) 17.0 (7.6)
Striped dolphin
227
225
68
65
66
3.5 (5.3)
2.9 (4.3)
4.4 (6.7)
6.0 (9.1)
Striped dolphin
227
225
68
65
66
3.5 (5.3)
2.9 (4.3)
4.4 (6.7)
6.0 (9.1)
(CV=9.4%)
(CV=9.4%) in
in April-September
April-September and
and 10.9
10.9 (CV=13.5%)
(CV=13.5%) in
in
October-March.
The
maximum
density
was
observed
observed in
in
October-March. The maximum density was
April-September with
with 0.87
0.87 individuals
individuals km
km-2
(CV=15.2%).
-2
-2 (CV=15.2%).
April-September
The
The density
density in
in winter
winter was
was somewhat
somewhat less
less than
than half
half of
of the
the
summer
density
at
0.37
(CV=21.7%),
with
a
significant
summer density at 0.37 (CV=21.7%), with a significant
difference
difference (Z-test=3.23,
(Z-test=3.23, p<0.005).
p<0.005).
Maximum lengths
lengths of
of stranded
stranded striped
striped dolphins
dolphins from
from the
the
Maximum
Mediterranean
Mediterranean were
were 227cm
227cm for
for males
males and
and 225cm
225cm for
for
females
females (from
(from 406
406 males
males and
and 327
327 females;
females; F.
F. Dhermain,
Dhermain,
GECEM
and O.
comm.).
GECEM and
O. Van
Van
Canneyt,
CRMM,
pers.
comm.).ofThe
The
GECEM
Van Canneyt,
Canneyt, CRMM,
CRMM -pers.
University
La
average
weights
computed
from
the
Trites
and
Pauly (1998)
(1998)
average
weights
computed
from
the
Trites
and
Pauly
Rochelle, pers. comm.). The average weights computed
from
regressions
65kg,
and
the
regressions
were
68kg
and
65kg, respectively,
respectively,
and65kg,
the
the
Trites andwere
Pauly68kg
(1998)and
regressions
were 68kg and
average
for
the
species
was
66kg
(Table
2).
average for and
the species
wasfor
66kg
respectively,
the average
the (Table
species 2).
was 66kg (Table 2).
-2
The
-2
The seasonal
seasonal biomass
biomass densities
densities were
were 57.6kg
57.6kg km
km-2
(CV=15.2%) in
in April-September
April-September and
and 24.5kg
24.5kg km
km-2
-2
-2
(CV=15.2%)
(CV=21.7%)
(CV=21.7%) in
in October-March
October-March (Fig.
(Fig. 3).
3). The
The average
average daily
daily
ration
ration for
for aa striped
striped dolphin
dolphin was
was estimated
estimated from
from the
the four
four
-1
different
models
to
range
from
2.9
to
6.0kg
d
(4.3-9.1%
-1
-1
different models to range from 2.9 to 6.0kg d (4.3-9.1% of
of
body mass,
mass, Table
Table 2),
2), with
with 4.4kg
4.4kg dd-1
estimated from
from Kenney
Kenney
-1
-1 estimated
body
et
et al.
al. (1997)
(1997) model.
model. The
The striped
striped dolphin
dolphin annual
annual consumption
consumption
-2
-1 (CV=17.7%):
rate
was
estimated
to
be
999kg
km
-2
-1 (CV=17.7%):
rate was estimated to be 999kg km-2 yy-1
492kg
492kg of
of fish;
fish; 497kg
497kg of
of cephalopods;
cephalopods; and
and 10kg
10kg of
of
crustaceans (Table
(Table 3).
3).
crustaceans
Risso’s
Risso’s dolphin
dolphin
Risso’s
dolphin sightings
sightings were
were truncated
truncated at
at 600m
600m and
and an
an esw
esw
Risso’s dolphin
of 430m
430m (CV=8.9%)
(CV=8.9%) was
was estimated
estimated using
using aa half-normal
half-normal
of
model.
model. Mean
Mean school
school size
size was
was 9.8
9.8 (CV=43.2%)
(CV=43.2%) in
in AprilAprilTable
Table 3
3
-2 -1
-2 -1
-2
-1
Seasonal
(kg
km
d
)
and
annual
-2
-1
-2 y
-1)
Seasonal (kg km d ) and annual (kg
(kg km
km-2
y-1
) estimates
estimates of
of consumption
consumption
of three categories of
prey
by
five
species
of cetaceans in the Ligurian Sea.
of three categories of prey by five species of cetaceans in the Ligurian Sea.
Species
Species
Sperm whale
Sperm whale
Pilot whale
whale
Pilot
Risso’s
Risso’s dolphin
dolphin
Striped
Striped dolphin
dolphin
All odontocetes
odontocetes
All
Fin whale
whale
Fin
All
All species
species
Prey
Prey
Fish
Fish
Cephalopods
Cephalopods
Fish
Fish
Cephalopods
Cephalopods
Fish
Fish
Cephalopods
Cephalopods
Fish
Fish
Cephalopods
Cephalopods
Crustaceans
Crustaceans
Fish
Fish
Cephalopods
Cephalopods
Crustaceans
Crustaceans
Fish
Fish
Crustaceans
Crustaceans
Fish
Fish
Cephalopods
Cephalopods
Crustaceans
Crustaceans
Total
Total
Season
Season
Apr.-Sep. Mar.-Oct.
Apr.-Sep. Mar.-Oct.
0.01
0.01
0.01
0.01
0.09
0.12
0.09
0.12
0.03
0.00
0.03
0.00
0.60
0.00
0.60
0.00
0.01
0.02
0.01
0.02
0.13
0.41
0.13
0.41
1.89
0.80
1.89
0.80
1.91
0.81
1.91
0.81
0.04
0.02
0.04
0.02
1.94
0.84
1.94
0.84
2.73
1.33
2.73
1.33
0.04
0.02
0.04
0.02
0.00
0.07
0.00
0.07
5.66
0.65
5.66
0.65
1.94
0.91
1.94
0.91
2.73
1.33
2.73
1.33
5.69
0.66
5.69
0.66
10.4
2.9
10.4
2.9
Annual
Annual
4
4
37
37
6
6
110
110
5
5
98
98
492
492
497
497
10
10
507
507
742
742
10
10
13
13
1,150
1,150
521
521
742
742
1,160
1,160
2,422
2,422
Fig. 3.
3. Estimated
Estimated biomass
biomass density
density (in
(in kg
kg km
km-2
) for
for each
each species
species for
for AprilApril-2
-2)
Fig.
September
(open
bars)
and
October-March
September (open bars) and October-March (filled
(filled bars)
bars) periods.
periods. Error
Error
bars
bars represent
represent the
the standard
standard errors.
errors.
September
September and
and 11.3
11.3 (CV=41.2%)
(CV=41.2%) in
in October-March.
October-March. These
These
results
lead
to
an
extrapolated
winter
an extrapolated winter density
density of
of 0.035
0.035
results lead to -2
(CV=58.2%), decreasing
decreasing to
to 0.011
0.011
individuals km
km-2
-2 (CV=58.2%),
individuals
(CV=58.9%)
(CV=58.9%) during
during summer.
summer. Risso’s
Risso’s dolphins
dolphins were
were the
the only
only
species
species with
with aa substantially
substantially higher
higher density
density in
in winter
winter than
than in
in
summer,
summer, differing
differing by
by aa factor
factor of
of about
about three,
three, but
but with
with no
no
significant difference
difference due
due to
to large
large CVs
CVs (Z-test=1.10,
(Z-test=1.10, p>0.30).
p>0.30).
significant
Maximum
Maximum lengths
lengths of
of Risso’s
Risso’s dolphin
dolphin from
from the
the French
French
Mediterranean
Mediterranean stranding
stranding network
network differed
differed by
by only
only 20cm
20cm
from
from the
the global
global values
values of
of 380cm
380cm for
for males
males and
and 360cm
360cm for
for
females reported
reported by
by Trites
Trites and
and Pauly
Pauly (1998)
(1998) and
and were
were based
based
females
on
on small
small sample
sample sizes
sizes (n<20
(n<20 for
for both
both males
males and
and females).
females).
Therefore
average
weights
were
used
for
males
Therefore average weights were used for males and
and females
females
as
as in
in Trites
Trites and
and Pauly
Pauly (1998);
(1998); 236kg
236kg and
and 211kg,
211kg, respectively.
respectively.
The average
average for
for the
the species
species was
was 224kg
224kg (Table
(Table 2).
2).
The
-2
The
-2
The seasonal
seasonal biomass
biomass densities
densities were
were 7.9kg
7.9kg km
km-2
-2
(CV=58.2%)
in
October-March
and
2.6kg
km
-2
(CV=58.2%) in October-March and 2.6kg km-2
(CV=58.9%)
in
April-September
(Fig.
3).
The
average
daily
(CV=58.9%) in April-September (Fig. 3). The average daily
ration for
for Risso’s
Risso’s dolphin
dolphin was
was estimated
estimated to
to range
range from
from 7.6
7.6 to
to
ration
-1 (3.4-7.6% of body mass, Table 2). From the
17.0kg
-1 (3.4-7.6% of body mass, Table 2). From the
17.0kg dd-1
36
LARAN et al.:
al.: SEASONAL
SEASONAL ESTIMATES
ESTIMATES OF
OF CETACEANS
CETACEANS IN
IN THE
THE LIGURUIAN
LIGURIAN SEA
LARAN et
selected model (Kenney et al., 1997) a value of 12.1kg d-1
was obtained. The annual consumption rate was estimated to
be 103kg km-2 (CV=65.3%): 5kg of fish; and 98kg of
cephalopods (Table 3).
Pilot whale
Most of the sightings of pilot whales occurred at
perpendicular distances of less than 800m; therefore a
uniform model was adopted, considering that all animals
were detected up to 800m from the transect. The species was
encountered in summer only, with a mean school size of
28.4 (CV=28.0%). The density was estimated as 0.027
individuals km-2 (CV=49.1%).
Maximum lengths of Mediterranean pilot whales were
600cm from 31 males and undetermined individuals and
500cm from 20 females (F. Dhermain, GECEM and O. Van
CRMM,- University
pers. comm.).
The average
weights
Canneyt, CRMM
of La Rochelle,
pers. comm.).
computed
from
the Trites
and Pauly
(1998)
regressions
were
The
average
weights
computed
from
the Trites
and Pauly
689kg regressions
and 451kg,were
respectively,
the respectively,
average for and
the
(1998)
689kg andand
451kg,
species
was for
546kg
(Table 2).
the
average
the species
was 546kg (Table 2).
The summer biomass density was 14.7kg km-2
(CV=49.1%) (Fig. 3). The average daily ration for pilot whales
was estimated from the four models to range from 15.5 to
34.2kg d-1 (2.8-6.3% of body mass, Table 2), with an estimate
from the selected model of 23.6kg d-1. The annual
consumption rate was estimated to be 116kg km-2
(CV=69.4%): 110kg of cephalopods; and 6kg of fish (Table 3).
Sperm whale
Sperm whale visual sightings and distinct acoustic
sequences represented a total of 27 encounters, including 20
detected only acoustically and 7 using both methods. Mean
school size was 1.5 (CV=10.5%) in summer and 3.0
(CV=29.6%) in winter. Their extrapolated density varied
between 3.9x10-4 individuals km² (CV=39.1%) in AprilSeptember and 5.2x10-4 (CV=38.6%) in October-March, the
smallest seasonal difference of any of the five species, with
no significant difference (Z-test=0.52, p>0.60).
The maximum length of sperm whales stranded along the
French Mediterranean coast was 15m from 18 males and
undetermined individuals (F. Dhermain, GECEM and O.
Van Canneyt, CRMM,
CRMM pers.
- University
La length
Rochelle,
comm.).ofThis
was pers.
also
comm.).
This30
length
was
also greater
than
length estimates
greater than
length
estimates
based
on 30
inter-pulse
interval
based
on inter-pulse
intervalrecordings
measurements
acoustic
measurements
from acoustic
in thefrom
northwestern
recordings
in the
Mediterranean
Sea (Drouot
Mediterranean
Seanorthwestern
(Drouot et al.,
2004). The average
male
et
al., 2004).
The average
weight and
computed
the
weight
computed
from male
the Trites
Paulyfrom
(1998)
Trites
and Pauly
(1998) As
regression
wasfemale
16.1t. As
only was
one
regression
was 16.1t.
only one
length
female
length
was available,
average
femalereported
weight by
of
available,
the average
femalethe
weight
of 10.1t
10.1t
by (1998)
Trites and
was used.
Trites reported
and Pauly
wasPauly
used.(1998)
The average
for The
the
average
for the
species
was
species was
12.5t
(Table
2).12.5t (Table 2).
The seasonal biomass densities were 4.9kg km-2
(CV=39.1%) and 6.6kg km-2 (CV=38.6%), in April-September
and October-March respectively (Fig. 3). The average daily
ration for sperm whales was estimated to range from 189 to
393kg d-1 (1.5-3.1% of body mass, Table 2). The daily ration
estimated from Kenney et al. (1997) model was 244kg d-1. The
annual consumption rate was estimated to be 41kg km-2
(CV=39.2%): 37kg of cephalopods; and 4kg of fish (Table 3).
Fin whale
An esw of 1,152m (CV=10.3%) was estimated for fin whales,
using a hazard-rate model without adjustment and after
truncation at 2,000m. Mean school size was 1.6 (CV=8.1%)
in April-September and 1.1 (CV=11.1%) in October-March.
The maximum density was observed in summer with 0.014
individuals km-2 (CV=19.2%), against 0.002 (CV=46.3%) in
winter. The 8-fold difference between seasonal densities was
the highest of any of the four species that were present in both
seasons and was significant (Z-test=4.35, p<0.0001).
The maximum length of Mediterranean fin whales was
20m, with no clear difference between males and females
(from 68 stranded individuals; F. Dhermain, GECEM and O.
comm.).ofThe
weights
Van Canneyt, CRMM,
CRMM pers.
- University
La average
Rochelle,
pers.
computedThe
from
the Trites
and Pauly
(1998)
regressions
comm.).
average
weights
computed
from
the Triteswere
and
31.4t for
malesregressions
and 30.8t for
females,
andmales
the average
for the
Pauly
(1998)
were
31.4t for
and 30.8t
for
species was
(Table for
2). the species was 31.1t (Table 2).
females,
and31.1t
the average
The seasonal biomass densities correspond to 429kg km-2
(CV=19.2%) in April-September and 54kg km-2 (CV=46.3%)
in October-March (Fig. 3). The average daily ration for a fin
whale was estimated to range from 393 to 680kg d-1 (1.32.2% of body mass; Table 2) and computed to be 410kg d-1
from the selected model. The annual consumption rate was
estimated to be 1,163kg km-2 (CV=25.2%): 1,150kg of
crustaceans; and 13kg of fish (Table 3).
All cetacean species
For all odontocetes combined, the biomass densities varied
(CV=19.2%)in
inwinter
winterand
and79.8kg
79.8kgkm
km-2between 38.9kg km-2-2(CV=19.2%)
2 (CV=14.5%)inin summer.
summer. The
The total
total cetacean
cetacean biomass
(CV=14.5%)
densities were 93.4kg km-2 (CV=28.2%) in winter and
509.0kg km-2 (CV=16.3%) in summer. These seasonal
values were significantly different (Z-test=4.9, p<0.0001).
The combined daily food consumption of all cetaceans
was estimated to be 2.9kg km-2 d-1 (CV=28.2%) in winter
(Table 3), dominated by cephalopods (45.9%), followed by
fish (31.3%) and crustaceans (22.8%). In summer, daily
consumption increased to 10.4kg km-2 d-1 (CV=16.3%),
strongly dominated by crustaceans (54.9%) and followed by
cephalopods (26.3%) and fish (18.7%). The seasonal
difference in prey types is driven by the different densities
of fin whales. Annual food requirement represents 2.4t km-2
(CV=20%) (Table 3, Fig. 4).
Fig. 4. Annual consumption rate (kg km-2 y-1) by cetaceans in the Ligurian
Sea compared to 2000-2005 average fishery landings and production
reported for Sardinia (FAO area 1.3) and the entire Mediterranean and
Black Sea.
Compared to reported fishery landings from either the
whole Mediterranean Sea or only the Sardinia region,
cetacean predation rates on crustaceans and molluscs are
much larger than fishery harvest rates (Fig. 4). Competition
for molluscs between cetaceans and humans is even lower
than apparent from the data because most of the species
consumed by teuthophageous odontocetes, particularly large
ones (Astruc, 2005), are not commercial species. Cetacean
consumption of fish is much closer to fish (including sharks)
harvest rates reported for the Sardinia area (202kg km-2) or
for the entire Mediterranean and Black Sea (437kg km-2 or
487 considering aquaculture).
MANAGE. 11(1):31–­­
11(1):31–40,
2009
J. CETACEAN
CETACEAN RES. MANAGE.
40, 2010
Primary production required
The primary production required to support total prey
consumption by cetaceans was estimated to be 12.6gC m-2
y-1. In the Ligurian Sea, the mean primary production has
been estimated at 165gC m-2 y-1, from SeaWiFS remotely
sensed imagery from 1998 to 2001 (Bosc et al., 2004). PPR
for cetaceans is 7.6% of that value. Total annual productivity
estimates from in situ 14C methods have varied from 86 to
226gC m-2 y-1 (Marty and Chiavérini, 1999), of which the
primary production requirement for cetaceans represents
between 5.6 and 14.7%.
DISCUSSION
This study estimates for the first time the seasonal
variability of density and biomass of cetaceans in the
Ligurian Sea, as well as their rates of prey consumption and
trophic effects. Although the results are sensitive to many
input parameters and assumptions, these results allow basic
comparisons in order of magnitude with reported fishery
landings and phytoplankton production. A recent document
from the European Community (COM, 2003) concluded
that despite an increase of the fishing effort in the
Mediterranean Sea overall production and rates have been
steadily decreased compared to the past. The approach
allows better quantification of the trophic importance of
cetaceans in the area and their fish demand than has been
available in the past.
Density
Both seasonal sampling periods were covered by more than
2,000km of survey effort, including at least 12 surveys over
the 4 years. The estimated densities for the two most
common species, striped dolphin and fin whale, should be
considered as reliable, which is supported by CVs of <22%
except for fin whales in winter. The estimate of summer fin
whale density (0.014 individuals km-2; CV=19.2%) is in
agreement with previous results, which vary from 0.015
individuals km-2 (CV=15.9%; Gannier, 1997) in the LiguroProvençal area to 0.024 individuals km-2 (CV=27.0%;
Forcada et al., 1996; Gannier, 1997) in the western
Mediterranean Sea. Fin whale density in the Ligurian Sea is
also similar to other regions of the North Atlantic, with 0.021
km-2-2 to
to 0.053
0.053(Buckland
(Bucklandetetal.,
al.,1992;
1992;
Kenney
individuals km
Kenney
et
et
al.,
1985)
Previousestimates
estimatesofof the
the summer
summer density of
al., 1985). Previous
striped dolphins in the area ranged between 0.30 individuals
km-2 (CV=35%) and 0.75 (Forcada and Hammond, 1998;
Gannier, 2006), with the minimum estimated just after an
epizootic mortality event. The estimate of 0.87 individuals
per km-2 (CV=15.2%) in April-September period is in
agreement, considering that previous estimates were
conducted in July and/or August, while in the data set used in
this study surveys were also carried out in September, which
corresponds to the maximum occurrence of striped dolphins
in the area (Laran and Drouot-Dulau, 2007). In the central
Spanish Mediterranean Sea, a maximum seasonal abundance
of 0.60 individuals per km-2 (CV=26.0%) was recorded in
Autumn (Gómez de Segura et al., 2006) – this is a wellknown productivity area (e.g. Cañadas and Hammond,
2006). These estimates are higher than the maximum density
estimate for any sampling stratum in the northwest Atlantic
(0.37 individuals per km-2; Kenney et al., 1985) or for small
delphinids in the Bay of Biscay (0.55 individuals per km-2,
CV=29%; Certain et al., 2008), however both studies were
based on aerial surveys and for the northwest Atlantic a much
higher proportion of small delphinid sightings was not
identified to species. In addition, striped dolphins in the
37
northwest Atlantic are known to be most abundant in waters
of the continental slope and farther offshore (Waring et al.,
2008), but the surveys reported by Kenney et al. (1985) were
almost entirely inshore of the shelf break.
The estimated densities for the less common species (sperm
whales, pilot whales and Risso’s dolphins) must be considered
with some caution, and the CVs are substantially larger in
most cases. For sperm whales, the annual encounter rate of
individuals was estimated to be 0.012 individuals km-1
(CV=55.0%), close to previous values; 0.006 individuals per
km (CV=44.0%; Gannier, 2006) or 0.007 (CV=21.7%;
Gannier et al., 2002) estimated in the same area. The estimated
densities of 5.2×10-4 individuals km-2 (CV=38.6%) in winter
and 3.9×10-4 (CV=39.1%) in summer obtained in this study
could only be compared with the rough estimate of 10×10-4 by
Gannier (1995), which considered visual sightings only. The
wide arbitrary distance (13km), on both sides of the transect,
to account for hydrophone efficiency may have led to an
underestimate of sperm whale density and is a factor that must
be better quantified for future work. For Risso’s dolphins, the
few existing estimates vary over the year from 0.015
individuals km-2 (CV=60.6%) for the central Spanish
Mediterranean (Gómez de Segura et al., 2006) to 0.021
(CV=37.1%) for the northwestern Mediterranean Sea
(Gannier, 1995). An estimated annual average of 0.023
individuals km-2 (CV=65.3%) was obtained in this study,
which is similar. There was a strong seasonal variation, with
winter density three times summer density, showing the
migratory behaviour of Risso’s dolphin in the area. For pilot
whales, the obtained sighting rate of 0.043 individuals km-1
(CV=49.1%) between April and September is quite low when
compared to the value of 0.14 whales km-1 (CV=69.3%)
obtained in the area in July-August 2001 (Gannier, 2006).
However the latter result was based on only a single sighting,
and both estimates have large variances. The estimated
summer density (0.027 individuals km-2; CV=49.1%) is
almost identical to the 0.028 (CV=62.3%) value computed
from the results of Gannier (1995).
Biomass and food consumption
Prior to the first dedicated surveys for cetaceans in the
Mediterranean Sea in the 1990s, biomasses of the eight most
common species were roughly estimated for the area between
40°N and European coasts (300,000km2) (table 13 in Viale,
1985). Interestingly, beginning from mean body mass
estimates that varied substantially from the values used in this
study and approximate numbers of animals in the area (with
no clear details available on those estimates), the author
calculated a total cetacean biomass of 86,950t, representing a
biomass density of 290kg km-2, very close to the estimate
obtained in this study (300kg km-2). In addition, Viale (1985)
estimated fish consumption of 58,100t, corresponding to
194kg km-2, while a value of 522 kg km-2 was obtained in this
study. For cephalopods her results corresponded to 763kg
km-2, and for macro- and microzooplankton, 1,100kg km-2,
while estimates of 739 and 1,160kg km-2 respectively were
obtained here. Since the methods and input parameters were
completely independent, this level of agreement is somewhat
encouraging. The better-supported estimates obtained through
this study, using better density values, also identify variations
between warm and cold seasons.
Comparisons with different studies and locations
The Mediterranean Sea, a semi-enclosed sea, has a lower
cetacean diversity than many other areas. Along the US
western coast, for example, about twenty cetacean species are
observed in the Californian Current ecosystem (Barlow et al.,
38
LARAN et al.:
al.: SEASONAL
SEASONAL ESTIMATES
ESTIMATES OF
OF CETACEANS
CETACEANS IN
IN THE
THE LIGURUIAN
LIGURIAN SEA
LARAN et
2008). Thirty-five species of cetaceans are known to occur
along the eastern coast of the US (Waring et al., 2008).
Estimates of biomass densities and prey consumption rates
allow for more informative comparisons with other areas than
is possible using only species abundances or densities. The
estimate of annual average biomass density obtained in this
study (301kg km-2) is intermediate between 143kg km-2 for
marine mammals in the entire Pacific Ocean (Trites et al.,
1997) and 729kg km-2 for cetaceans only in the northeastern
US continental shelf system (Kenney et al., 1997). During
summer and autumn, Barlow et al. (2008) estimated a value of
282kg km-2 for cetacean biomass density in the California
current ecosystem, with a proportion of Balaenopteridae
(70%) similar to the observations noted in this paper. Seasonal
variability was somewhat stronger in the Ligurian Sea than in
the NE US shelf; the results detailed here differ by a factor of
five between six-month winter and summer seasons, while
Kenney et al. (1997) reported a maximum ratio of 3.8 between
winter and spring. In agreement with the results of the study
presented here and those of Barlow et al. (2008), Kenney et al.
(1997) showed a cetacean community dominated by
balaenopterids, at 72-78% of the total standing stock, but their
dominance continued through all four seasons of the year.
-2 -2
The
estimateofoffood
foodintake
intakebybycetaceans
cetaceans
(2.4t
The point
point estimate
(2.4t
kmkm
y-1
-1
y this
in this
study)
muchgreater
greaterthan
thanresults
results for
for northern
in
study)
is is
much
European seas, ranging between 0.25t km-2 y-1 in Atlantic
waters to 0.75 around Spitsbergen and in polar waters
(Joiris, 1992; 1996; 2000). Prey consumption estimates
from the studies discussed immediately above, as expected,
follow the same order as the estimates of biomass density.
-2 -2
Barlow
of of
1.5-2.4t
kmkm
y-1
Barlow etet al.
al. (2008)
(2008)reported
reportedconsumption
consumption
1.5-2.4t
-1
in
California
current,
thethemost
y the
in the
California
current,
mostsimilar
similarvalue
valuetoto that
that of
this study; the minimum was 0.84t km-2 y-1 in Pacific Ocean
(Trites et al., 1997) and the maximum was 6.7t km-2 y-1 on
the northeastern US continental shelf (Kenney et al., 1997).
Estimates of fish consumption by marine mammals vary
from 0.10t km-2 y-1 in the North Sea to 5.4t km-2 on Georges
Bank (Bax, 1991), and the point estimate obtained here of
0.48t km-2 y-1 of fish consumed corresponds to the lower
end of that range. Kenney et al. (1997) estimated fish
consumption
higher
at 4.6t
km-2km
y-1consumptiontotobebeananorder
orderofofmagnitude
magnitude
higher
at 4.6t
2 y-1 because
because
the diet
of fin,
humpback
the diet
of fin,
humpbackand
andminke
minkewhales
whales off
off
the northeastern US is primarily fish rather than crustaceans.
World
rates
vary
between
10 and
km-2
Worldfishery
fisherycatch
catch
rates
vary
between
10 22.2t
and 22.2t
-2
-1
-1
y (from
oligotrophic
open-ocean
km
y (from
oligotrophic
open-oceansystems
systemstoto highly
highly
productive upwellings)
upwellings) representing
total net
net
productive
representing 1.8-35%
1.8-35% of
of the
the total
primary production (Pauly and Christensen, 1995).
Compared with commercial fisheries, the point estimate of
the relative proportion of fish consumed by marine mammals
represents some 2% of the fisheries in the North Sea (Bax,
1991), 167% in the Barents Sea (Bax, 1991) and 171% in the
northeastern US shelf (Kenney et al., 1997). About 150%
was estimated for herring only in the Gulf of Maine
(Overholtz and Link, 2006). In the Ligurian Sea, the point
estimate of the proportion of fish consumed by cetaceans
represents 257% of the reported fishery if only the Sardinia
area is considered and 107% compared to global production
of fisheries (i.e. catches and aquaculture combined) from the
entire Mediterranean Sea. Since a large proportion of the fish
harvested remains unrecorded, relative percentages of
cetacean consumption should probably be reduced compared
to actual catches. In the Pacific Ocean, Trites et al. (1997)
estimated that fisheries target only 35% of the prey items
sought by marine mammals. However this ratio could vary
between predator species; for example 70% of the total prey
species of striped and Risso’s dolphins in the Mediterranean
are commercial species (Würtz et al., 1992).
The primary production required for cetaceans was
estimated as 20-30gC m-2 y-1 in the Pacific Ocean (Trites et
al., 1997), 31.4gC m-2 y-1 in the California Current ecosystem
(Barlow et al., 2008) and 47.5gC m-2 y-1 in the northeastern
US shelf ecosystem (Kenney et al., 1997), all higher than the
estimate of 12.6 obtained here. The mathematical model used
to estimate PPR (Eqn. 8) includes a power function, so the
PPR estimates are especially sensitive to the trophic level of
the prey species and the most difficult result to compare
between ecosystems.
ecosystems. Following
FollowingBarlow
Barlowetetal.al.(2008),
(2008),whom
who
conducted sensitivity analysis in a similar study in the
California area, the main effect on approximation of result is
the energy transfer across the food web.
Potential sources of variability and error
In the area used in this study, further investigation is
necessary to derive more reliable density estimates for less
common species such as sperm whales, pilot whales and
Risso’s dolphins, in addition to the rarer or coastal species that
were not sampled at all during the surveys. In addition, there
is a negative bias caused by not considering g(0). For the fin
whale, no decrease in detection probability on the line was
recorded between fast and reduced-speed sampling (22 and
13km h-1), in contrast with the striped dolphin for which a
decrease of 12% was estimated at 22km h-1 (Laran, 2005).
Therefore there was probably an underestimation of striped
dolphin density. For the sperm whale, acoustic sampling
allowed detection of clicks during almost all their dive
durations (Mullins et al., 1988), but the efficiency of the
hydrophone likely varies with water column conditions,
instead of remaining constant at the arbitrary sampling width
of 13km. In addition, the sampling protocol allowed monthly
effort to be maintained during three years, but was not suited
to estimation of cetacean abundance in the entire Pelagos
Sanctuary. Additional field campaigns over broader areas of
the Sanctuary, dedicated to abundance estimation, should be
carried out in summer and winter to obtain accurate estimates.
Previous studies of this type (Kenney et al., 1985; Kenney
et al., 1997; Sigurjónsson and Víkingsson, 1997; Trites and
Pauly, 1998) generally have relied on relatively imprecise
estimates of body mass available from the literature as the
starting point for bioenergetic models. Kenney et al. (1985)
had reliable data from their own study area for only one
species, using a set of photogrammetric length measurements
of fin whales and a published weight-length equation to
derive a mean weight for the study region. Trites and Pauly
(1998) have assisted researchers developing marine mammal
energetic models by presenting estimates of average body
weights for all species, although they did not provide
estimates of variability. Finally, using maximum lengths
observed within a particular area, when available, enables the
modelling results to better represent the local or regional
system. Large datasets of body weights from a particular
region would allow direct estimation of mean weights and
variability, although it becomes more difficult with
increasing body size and there are concerns over bias if the
data are obtained from strandings.
Another important source of uncertainty in the results is
prey consumption rate. The mean daily rations estimated as
percentages of an individual’s body mass (1.3-6.7% using
the selected model and 1.3-9.1% across all four models) are
consistent with general approximations of 3 to 5% for
marine mammals (Trites, 2003). The model used here was
intermediate in value, and was the model proposed by
Barlow et al. (2008) to be the most realistic. Fin whale daily
intake has been estimated as 1.3-3.3% of body mass from
various methods (Lockyer, 1981; 2007), but the estimates
MANAGE. 11(1):31–­­
11(1):31–40,
2009
J. CETACEAN
CETACEAN RES. MANAGE.
40, 2010
39
J. CETACEAN
RES. MANAGE.
11(1):31–40,
2009
39
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